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Synthesis of cobalt and iron based metal organic frameworks and their applications

TU N. THACH

CONTENTS
INTRODUCTION ............................................................................................................... 1
CHAPTER 1: THE CHEMISTRY & APPLICATIONS OF METAL ORGANIC
FRAMEWORKS .................................................................................................................. 3
1.1

Definition of Metal Organic Framework ................................................................ 3

1.2

Applications of Metal-organic Frameworks .......................................................... 4

1.2.1

Applications of Metal organic Frameworks as Heterogeneous Catalysis .............. 4

1.2.1.1 Metal-organic Frameworks as Scaffold for Oxidative Transformation of Organic
Substrates .............................................................................................................................. 5
1.2.1.1.1


Cobalt-based MOFs for Oxidative Transformation of Small Organic

Substrates .............................................................................................................................. 5
1.2.1.1.2

Metal-organic Frameworks for Oxidative Conversation of Large Organic

Substrates .............................................................................................................................. 7
1.2.1.2 Strategy for Design the Catalytic Active Centers in MOFs ................................... 9
1.2.1.2.1

Metal Clusters as the Catalytic Active Sites in MOFs ................................... 9

1.2.1.2.2

Functional Linkers as Catalytic Active Sites in MOFs ................................ 10

1.2.1.2.3

Post-Modification Strategy for Incorporating Catalytic Active Sites into

MOFs .................................................................................................................................. 12
1.2.1.2.4
1.2.2

Immobilization of Catalytic Active Guests into MOFs via Self-Assembly . 13

MOFs for Proton Conduction ............................................................................... 15

1.2.2.1 Water-mediated Proton Conducting MOFs .......................................................... 16
1.2.2.1.1

Design Strategy toward High Proton Conductivity MOFs under Humidity

Condition............................................................................................................................. 16
1.2.2.1.1.1

Doping Proton Donors Molecules into the MOFs ........................................ 16


1.2.2.1.1.2

Coordinately Unsaturated Metal Sites Approach ......................................... 17
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1.2.2.1.1.3

Acidic Functional Groups Approach ............................................................ 17

1.2.2.1.1.4

Defect Sites Approach .................................................................................. 18

1.2.2.1.1.5

Water-mediated Proton Conductivity of MOFs .......................................... 18

1.2.2.2 Anhydrous proton-conducting MOFs ................................................................... 20
CHAPTER 2: SYNTHESIS OF THE NOVEL METAL-ORGANIC FRAMEWORKS
AND MATERIAL CHARACTERIZATIONS .................................................................. 22
2.1

Introduction ........................................................................................................... 22

2.1.1

The Modular Nature in Design and Synthesis of MOFs and The Quest to Design

and Synthesize New MOFs................................................................................................. 22
2.1.2

Objective ............................................................................................................... 24

2.1.3

Approach ............................................................................................................... 24

2.2

Materials and Instrumentation ............................................................................. 24

2.2.1

Materials................................................................................................................ 24

2.2.2

Single Crystal X-ray Diffraction (SC-XRD) and Powder X-ray Diffraction (PXRD)

Data Collection ................................................................................................................... 25
2.2.3

Instruments for Characterization of VNU-10, VNU-15, Fe-NH2BDC, Fe-BTC. 26

2.3

Material Synthesis, Single Crystal Structure Analysis and Characterization for

VNU-10............................................................................................................................... 27
2.3.1

Synthesis of VNU-10 ............................................................................................ 27

2.3.2

Crystal Structure of VNU-10 ................................................................................ 27

2.3.3

Characterization of VNU-10 ................................................................................. 31

2.3.3.1 Microscope Image of VNU-10 ............................................................................. 31
2.3.3.2 PXRD Analysis of VNU-10.................................................................................. 31
2.3.3.3 FT-IR Analysis of activated VNU-10 ................................................................... 32

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2.3.3.4 Thermogravimetric Analysis of VNU-10 ............................................................. 33
2.3.3.5 Gas Adsorption Measurements ............................................................................. 33
2.4

Material Synthesis, Single Crystal Structure Analysis and Characterization for the

Novel structure of VNU-15 ................................................................................................ 35
2.4.1

Synthesis of VNU-15 ............................................................................................ 35

2.4.2

Crystal Structures of VNU-15 .............................................................................. 36

2.4.3

Characterization of VNU-15 ................................................................................. 40

2.4.3.1 Microscope Image of VNU-15 ............................................................................. 40
2.4.3.2 PXRD Analysis for VNU-15 ................................................................................ 40
2.4.3.3 FT-IR Analysis of activated VNU-15 ................................................................... 41
2.4.3.4 Thermogravimetric Analysis of VNU-15 ............................................................. 42
2.4.3.5 Porosity and Gas Adsorption of VNU-15 ............................................................. 43
2.4.3.6 Water Uptake, PXRD and FT-IR of Corresponding VNU-15 Sample ................ 45
2.5

Material Synthesis, Single Crystal Structure Analysis and Characterization for the

Novel structure of Fe-NH2BDC .......................................................................................... 46
2.5.1

Synthesis of Fe-NH2BDC ..................................................................................... 46

2.5.2

Crystal Structures of Fe-NH2BDC ........................................................................ 47

2.5.3

Characterization of Fe-NH2BDC .......................................................................... 50

2.5.3.1 Microscope Image of Fe-NH2BDC ....................................................................... 50
2.5.3.2 PXRD Analysis of Fe-NH2BDC ........................................................................... 50
2.5.3.3 FT-IR Analysis of activated Fe-NH2BDC ............................................................ 51
2.5.3.4 Thermogravimetric Analysis of Fe-NH2BDC ...................................................... 51
2.6

Material Synthesis, Single Crystal Structure Analysis and Characterization for the

Novel structure of Fe-BTC ................................................................................................. 52
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2.6.1

Synthesis of Fe-BTC ............................................................................................. 52

2.6.2

Crystal Structures of Fe-BTC ............................................................................... 53

2.6.3

Characterization of Fe-BTC .................................................................................. 55

2.6.3.1 PXRD Analysis of Fe-BTC .................................................................................. 55
2.6.3.2 Thermogravimetric Analysis of Fe-BTC .............................................................. 56
CHAPTER 3: APPLICATIONS OF VNU-10 AND VNU-15 ........................................... 57
3.1

NEW

TOPOLOGICAL

HETEROGENEOUS

CATALYST

Co2(BDC)2(DABCO)
FOR

AMINATION

AS
OF

HIGHLY

ACTIVE

OXAZOLES

VIA

OXIDATIVE C-H/N-H COUPLINGS ............................................................................... 57
3.1.1

The Quest for Large Pore Window (above 15 Å) and High Surface Area (above

2600 m2 g-1) MOFs as Catalyst for Large Substrate Conversions ...................................... 57
3.1.2

Direct Amination of Azoles under Mild Reaction Conditions ............................. 58

3.1.3

Objective ............................................................................................................... 59

3.1.4

Approach ............................................................................................................... 59

3.1.5

Method for Catalysis Study .................................................................................. 60

3.1.5.1 Method for Gas Chromatographic ........................................................................ 60
3.1.5.2 GC Calculation and analysis ................................................................................. 61
3.1.5.3 Method for Catalytic studies ................................................................................. 61
3.1.5.4 Synthesis of Reported MOFs ................................................................................ 62
3.1.6

Investigations on VNU-10 Catalytic Performance for Direct Oxidative Amination

of Benzoxazole with Piperidine .......................................................................................... 62
3.1.6.1 Conditions Screening for Direct Oxidative Amination of Benzoxazole with
Piperidine Using Heterogeneous VNU-10 ......................................................................... 62
3.1.6.1.1

Effect of Reagent Ratio on GC Yield ........................................................... 63

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3.1.6.1.2

Effect of Catalyst Loading on GC Yield ...................................................... 64

3.1.6.1.3

Effect of Various Solvents on GC Yield ...................................................... 65

3.1.6.1.4

Effect of Various Acids on GC Yield ........................................................... 66

3.1.6.1.5

Effect of Various Oxidants on GC Yield ..................................................... 68

3.1.6.1.6

Optimizing Condition for Amination of Benzoxazole Reaction Using VNU-

10 Catalyst & Product Analysis by 1H-NMR and 13C-NMR ............................................. 70
3.1.6.2 Advantages of VNU-10 for Amination of Benzoxazole Reaction over Other
Heterogeneous and Homogeneous Catalyst ....................................................................... 71
3.1.6.3 The Heterogeneous Nature of VNU-10 ................................................................ 74
3.1.6.4 Greener Protocol to Benzoxazole Amine Compounds by Recycling of VNU-10
............................................................................................................................................. 76
3.1.6.5 Synthesis of Diverse Benzoxazole Amine Derivatives with Different Amine
Substitutes ........................................................................................................................... 78
3.2

HIGH PROTON CONDUCTIVITY AT LOW RELATIVE HUMIDITY IN AN

ANIONIC Fe-BASED METAL-ORGANIC FRAMEWORK ........................................... 80
3.2.1

Introduction of Hydrogen Fuel Cell, Impedance and Nyquist Plot of Impedance

............................................................................................................................................. 80
3.3.1.1 Hydrogen Fuel Cell ............................................................................................... 80
3.3.1.2 Definition of Impedance and Nyquist Plot of Impedance .................................... 82
3.2.2

The Quest of Proton Conducting Membrane that Maintain High Conductivity at

High Temperature and Low Humidity ............................................................................... 83
3.2.3

Objectives.............................................................................................................. 84

3.2.4

Approach ............................................................................................................... 84

3.2.5

Method for Proton Conductivity Measurement .................................................... 84

3.2.5.1 Preparation of Pelletized VNU-15 and Proton Conductivity Measurement ......... 84
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3.2.5.2 Data Proceeding to Obtain Proton Conductivity .................................................. 85
3.2.6

Investigation for the Proton Conductivity of VNU-15 ......................................... 86

3.2.6.1 Correlation between Structure of VNU-15 and Proton Conductivity .................. 86
3.2.6.2 Proton Conductivity Measurement of VNU-15 under Low Humidity at 95 °C ... 87
3.2.6.3 Exploration of the Proton Conduction Mechanism of pelletized VNU-15 .......... 89
3.2.6.4 Investigation for the Stability of VNU-15 during Proton Conductivity
Measurement ...................................................................................................................... 92
3.2.6.5 Investigation for the Working Stability of VNU-15 as Function of Time &
Conductivities under 55 and 60% RH at 95 °C .................................................................. 95
CONCLUSION ................................................................................................................... 97
List of Publications ............................................................................................................. 99
References ......................................................................................................................... 100

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List of Figures
Fig. 1 Structure of MOF-5 constructed from Zn4O(CO2)6 cluster and BDC2- linker .... 3
Fig. 2 Recent progress on synthesizing high surface area material. .............................. 3
Fig. 3 a) Crystal structure of PCN-222; b) Peroxidase-like oxidation reaction of
pyrogallol catalyzed by PCN-222(Fe) ........................................................................... 7
Fig. 4 a) Crystal structure of PCN-600(Fe); b) Enzyme mimetic co-oxidation of phenol
and 4-aminoantipyrine catalyzed by PCN-600(Fe). ...................................................... 8
Fig. 5 a) [Co4Cl]7+ secondary building unit and the crystal structure of Co-btt; b)
Epoxides ring opening reaction carried out by Co-btt catalysis .................................... 9
Fig. 6 a) Crystal structure of ZIF-9; b) The CO2 reduction reactions catalysis by ZIF-9.
...................................................................................................................................... 10
Fig. 7 a) Structure of ZnPO-MOF and corresponding linker to construct the MOF; b)
Mechanism for acyl-transfer reaction catalyze by ZnPO-MOF .................................. 11
Fig. 8 a) Urea MOF strategy; b) Catalytic activities of NU-601. ................................ 12
Fig. 9 a) Post-modified MIL-101 by sequent combination between Brønsted acid and
Lewis acid sites; b) Investigated the benzylation reaction of mesitylene with benzyl
alcohol; c) Compared catalytic activity of MIL-101-Cr-SO3H·Al(III) with other
catalysts. ....................................................................................................................... 12
Fig. 10 One-Pot Synthesis of the MIL101-Anchored Nickel Complex, Ni@(Fe)MIL101................................................................................................................................ 13
Fig. 11 a) Crystal structure of rho-ZMOF with schematic presentation of [H2TMPyP]4+
porphyrin ring enclosed in rho-ZMOF α-cage, b) Cyclohexane catalytic oxidation at 65
°C. Yield % based on TBHP, 1 eq. consumed per alcohol produced and 2 eq. consumed
per ketone produced ..................................................................................................... 14
Fig. 12 X-rays crystal structure of CuPW11O39]5-@HKUST-1 ................................... 15
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Fig. 13 Structure of VNU-10, the paddle wheel cluster are connected with BDC2- by
two different way to form the DABCO connected kgm layers of VNU-10 and DABCO
connected sql layer of Co2(BDC)2(DABCO). C, black; O, red; Co, light blue; N, blue;
H was omitted for clarity. ............................................................................................ 28
Fig. 14 Crystal structure of VNU-10 represented in DABCO connected kgm layers; a)
Vertexes and edges assignment for cobalt nodes and linkages of VNU-10; b) Structure
of VNU-10 represented in DABCO connected kgm layers. Black, BDC2-; Blue,
DABCO; light blue, paddle wheel cobalt nodes; yellow, linkages between iron nodes.
...................................................................................................................................... 28
Fig. 15 Thermal ellipsoid plot of the asymmetric unit of VNU-10 with 30% probability.
C, black; O, red; Co, light blue; N, blue; H, white. ..................................................... 29
Fig. 16 Green needle crystal of VNU-10 at forty zooming times. .............................. 31
Fig. 17 The calculated PXRD pattern of VNU-10 from single crystal data (red)
compared with the experimental patterns from the as-synthesized VNU-10 (orange) and
Co2(BDC)2DABCOsql (Black). .................................................................................... 32
Fig. 18 FT-IR of activated VNU-10; inset: zooming with wavelength from 1450 to 1690
cm-1. ............................................................................................................................. 32
Fig. 19 Thermogravimetric analysis of VNU-10 in air stream under 20% O2 and
80% N2. ....................................................................................................................... 33
Fig. 20 N2 adsorption isotherm of VNU-10 at 77 K.................................................... 34
Fig. 21 CO2, CH4, N2 adsorption isotherm of VNU-10 at 273 K. ............................... 34
Fig. 22 CO2, CH4, N2 adsorption isotherm of VNU-10 at 298 K. ............................... 35
Fig. 23 Crystal structure of VNU-15 is constructed from BDC2- and NDC2- linkers that
stitch together corrugated infinite rods of [Fe2(CO2)3(SO4)2(DMA)2]∞ (a). These
corrugated infinite rods propagate along the a and b axes to form the three-dimensional
architecture. The structure is shown from the [110] and [001] plans (b, c, respectively).
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Atom colors: Fe, orange and blue polyhedra; C, black; O, red; S, yellow; N, blue; and
DMA cations, light blue. All other H atoms are omitted for clarity. ........................... 37
Fig. 24 Representation of the fob topology that VNU-15 adopts. a) Vertexes and edges
assignment for iron nodes and linkages of VNU-15; b) Structure of VNU-15
represented in fob topology. Atom colors: Fe, orange and blue polyhedra; C, black; O,
red; S, yellow; N, blue; and DMA cations, light blue. All other H atoms are omitted for
clarity. .......................................................................................................................... 38
Fig. 25 Thermal ellipsoid plot of the asymmetric unit of VNU-15 with 50% probability.
C, black; O, red; Fe, orange; S, yellow; N, blue; H, white. ......................................... 40
Fig. 26 Orange octahedral crystal of VNU-15 at forty zooming times. ...................... 40
Fig. 27 The calculated PXRD pattern of VNU-15 from single crystal data (black)
compared with the experimental patterns from the as-synthesized sample (blue) and
samples after activation at 100 °C (red). ..................................................................... 41
Fig. 28 FT-IR spectra of activated VNU-15. ............................................................... 42
Fig. 29 Thermogravimetric analysis of VNU-15 in air stream with 20% O2 and 80%
N2. ................................................................................................................................ 42
Fig. 30 CO2, CH4, N2 adsorption isotherm of VNU-15 at 298 K. ............................... 43
Fig. 31 CO2, CH4, N2 adsorption isotherm of VNU-15 at 273 K. ............................... 44
Fig. 32 Water uptake of VNU-15 at 25 °C as a function of P/P0 ranging from 8% to
80%. Inset: Water uptake of VNU-15 at 25 °C with P/P0 ranging from 8% to 62.58%.
...................................................................................................................................... 45
Fig. 33 PXRD analysis of VNU-15 exhibiting the long range order of the structure was
retained after water uptake up to 60% RH at 25 °C. The experimental pattern (red)
corresponded well with the simulated (black) diffraction pattern of VNU-15 from single
crystal data. .................................................................................................................. 45

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Fig. 34 FT-IR spectra of VNU-15, post H2O uptake at 60% RH, as compared with
activated VNU-15. ....................................................................................................... 46
Fig. 35 Structure of Fe-NH2BDC: a) Fe2(CO2)4(SO4)2 clusters were connected by NH2BDC to form Fe-NH2BDC; b) Connected sql layers through hydrogen bond between
(CH3)2NH2+ and sulphate ligand; c) Crystal structure of Fe-NH2BDC represents in sql
layers. Atom color: C, black; O, red; Fe, orange polyhedra; S, yellow; N, blue; H of
nitrogen, white; H atoms connected to carbon are omitted for clarity. ....................... 47
Fig. 36 Thermal ellipsoid plot of the asymmetric unit of Fe-NH2BDC with 30%
probability. C, black; O, red; Fe, orange; S, yellow; N, blue; H, white; Cu green...... 48
Fig. 37 Orange blocked crystal of Fe-NH2BDC at eighty zooming times. ................. 50
Fig. 38 The calculated PXRD pattern of Fe-NH2BDC from single crystal data (black)
compared with the experimental patterns from the as-synthesized sample (red). ....... 50
Fig. 39 FT-IR of activated Fe-NH2BDC. .................................................................... 51
Fig. 40 Thermogravimetric analysis of activated Fe-NH2BDC in air stream with 20%
O2 and 80% N2. ............................................................................................................ 52
Fig. 41 Crystal structure of Fe-BTC is constructed from BTC3- linkers and two different
SBU: tetrahedral single iron atom SBU and the iron paddle wheel SBU (a); The crystal
structure of Fe-BTC viewed along [001] plan (b); The mmm-a topology of Fe-BTC
(c). Atom colors: Fe, blue polyhedra; C, black. All other H atoms are omitted for clarity.
Atom colors: Fe, blue polyhedra; C, black; O, red; S, yellow; N, blue; and DMA cations,
light green. All other H atoms are omitted for clarity. ................................................ 53
Fig. 42 Thermal ellipsoid plot of the asymmetric unit of Fe-BTC with 30% probability.
C, black; O, red; Fe, orange; S, yellow; N, blue; H, white. ......................................... 55
Fig. 43 The calculated PXRD pattern of Fe-BTC from single crystal data (black)
compared with experimental patterns from the as-synthesized sample (red). ............. 55

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Fig. 44 Thermogravimetric analysis of activated Fe-BTC in air stream with 20% O2 and
80% N2. ........................................................................................................................ 56
Fig. 45 Effect of benzoxazole/piperidine molar ratio on GC yield of 2-(piperidin-1yl)benzoxazole. ............................................................................................................ 63
Fig. 46 Effect of VNU-10 catalyst molar on GC yield of 2-(piperidin-1-yl)benzoxazole.
...................................................................................................................................... 65
Fig. 47 Effect of reaction solvent on GC yield of 2-(piperidin-1-yl)benzoxazole. ..... 66
Fig. 48 Effect of different types of proton donor on GC yield of 2-(piperidin-1yl)benzoxazole. ............................................................................................................ 67
Fig. 49 Effect of acetic acid amount on GC yield of 2-(piperidin-1-yl)benzoxazole. 67
Fig. 50 Effect of different oxidants on GC yield of 2-(piperidin-1-yl)benzoxazole. .. 69
Fig. 51 Effect of TBHP on GC yield of 2-(piperidin-1-yl)benzoxazole. .................... 69
Fig. 52 1H-NMR spectrum of 2-(piperidin-1-yl)benzoxazole products. ..................... 70
Fig. 53 13C-NMR spectrum of 2-(piperidin-1-yl)benzoxazole products. .................... 71
Fig. 54 Different MOFs as catalyst for the direct benzoxazole amination reaction. ... 72
Fig. 55 Difference in activity between VNU-10 and cobalt salts as catalyst for the direct
benzoxazole amination reaction................................................................................... 73
Fig. 56 Compare activity of VNU-10 with smaller pore MOFs, zeolite, oxide & cobalt
salts as catalyst for the direct benzoxazole amination reaction. .................................. 74
Fig. 57 Leaching test with catalyst removal during reaction course. Conversion
percentage as a function of reaction time in the presence of the VNU-10 catalyst (filled
circle) and once VNU-10 was removed 5 min after the reaction started (open circle).
...................................................................................................................................... 75
Fig. 58 Investigate the recycling ability of VNU-10 catalyst. ..................................... 77
Fig. 59 Coincided PXRD of the fresh and reused VNU-10. ....................................... 77
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Fig. 60 Coincided FT-IR of the fresh and reused VNU-10. ........................................ 78
Fig. 61 Conversion of benzoxazole to diverse benzoxazole amine derivatives under
optimized conditions using different amines moieties. ............................................... 79
Fig. 62 Typical structure of Hydrogen fuel cell. ......................................................... 80
Fig. 63 Typical Nyquist plot and an equivalent circuit used for fitting. Schematic
representations: Rc/Rm, resistor; W, Warburg diffusion element; C, capacitor. ........... 82
Fig. 64 An equivalent circuit used for fitting. Schematic representations: R1/R2/R3,
resistor; W1, Warburg diffusion element; Q1/Q2/Q3, imperfect capacitor. .................. 85
Fig. 65 Nyquist plot derived from equivalent circuit (black line) and experimental
Nyquist plot (blue circles) of pelletized VNU-15 under 60% RH at 25 °C. Frequency
ranged from 1 MHz to 10 Hz. Inset: Zoom of Nyquist plot at high frequency. .......... 85
Fig. 66 Nyquist plot derived from equivalent circuit (black line) and experimental
Nyquist plot (blue circles) of pelletized VNU-15 under 60% RH at 95 °C. Frequency
ranged from 1 MHz to 10 Hz. Inset: Zoom of Nyquist plot at high frequency. .......... 86
Fig. 67 Nyquist plots of pelletized VNU-15 under 30% RH at 95 °C (red circles). Inset:
Nyquist plots of pelletized VNU-15 under 40% RH (brown circles), 50% RH (green
circles) and 55% RH (blue circles) at 95 °C. ............................................................... 87
Fig. 68 Dependence of proton conductivity in VNU-15 as a function of relative
humidity at 95 °C. Inset: Nyquist plot of VNU-15 at 60% RH. .................................. 88
Fig. 69 Nyquist plots resulting from ac impedance analysis of VNU-15 under 55% RH
when heating and cooling from 25 ºC to 95 ºC. .......................................................... 90
Fig. 70 Nyquist plots resulting from ac impedance analysis of VNU-15 under 60% RH
when heating and cooling from 25 ºC to 95 ºC. .......................................................... 91
Fig. 71 Arrhenius plot of VNU-15 under 55 and 60% RH at elevated temperature. .. 92
Fig. 72 Simulated PXRD pattern of VNU-15 (black) as compared to the experimental
patterns from the pelleted VNU-15 (red) and subjecting pelleted VNU-15 to 30, 40, and
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50% RH for 16 hours at each RH followed by ac impedance analysis at temperatures
ranging from 25 to 95 ºC (blue). .................................................................................. 93
Fig. 73 FT-IR of activated VNU-15 (black) as compared to the experimental spectrum
after subjecting pelleted VNU-15 to 30, 40, and 50% RH for 16 hours at each RH
followed by ac impedance analysis at temperatures ranging from 25 to 95 ºC (red). . 93
Fig. 74 Simulated PXRD pattern of VNU-15 (black) as compared to the experimental
patterns from pelleted VNU-15 (red) and subjected to 60% RH for 16 hours followed
by ac impedance analysis (green). ............................................................................... 94
Fig. 75 FT-IR of activated VNU-15 (black) as compared to the experimental spectra
of pelletized VNU-15 that was subjected to 60% RH for 16 hours followed by ac
impedance analysis at 25 ºC (red) and 95 ºC (blue). ................................................... 94
Fig. 76 Nyquist plot of VNU-15 at 55 (blue circles) and 60% RH (red circles) at 95 ºC
after 40 h of consecutive ac impedance measurements. .............................................. 95
Fig. 77 Time-dependent proton conductivity of VNU-15 at 55% RH (blue circles)
and 60% RH (red circles) and 95 ºC. ....................................................................... 95

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List of Tables
Table 1 Published MOFs for water-mediated proton conduction and its
conductivity. ............................................................................................................... 18
Table 2 Published MOFs for anhydrous proton conduction and its conductivity. ..... 21
Table 3 Famous MOFs that was synthesized by commercial linkers. ........................ 23
Table 4 Crystal data and structure refinement for VNU-10. ...................................... 30
Table 5 CO2, CH4, N2 uptake at 802 Torr and selectivity in adsorption of CO2 over CH4
and N2 of VNU-10 ....................................................................................................... 35
Table 6 Crystal data and structure refinement for VNU-15. ...................................... 39
Table 7 CO2, CH4, N2 uptake at 802 Torr and selectivity in adsorption of CO2 over CH4
and N2........................................................................................................................... 44
Table 8 Crystal data and structure refinement for Fe-NH2BDC. ................................ 49
Table 9 Crystal data and structure refinement for Fe-BTC. ....................................... 54
Table 10 Catalyst and window aperture ...................................................................... 72
Table 11 Relative humidity & proton conductivity dependence of VNU-15 at 95 ºC.
...................................................................................................................................... 88
Table 12 Proton conductivity of VNU-15 in comparison with other water-mediated
ultrahigh proton conducting MOFs. ............................................................................ 89
Table 13 Temperature & proton conductivity dependence of VNU-15 at 55 and 60%
RH. ............................................................................................................................... 91

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List of Schemes
Scheme 1 Formation of the observed products through the reaction of tert-butyl peroxy
radicals with cyclohexene. (b) Mechanism for the formation of tert-butylperoxy radicals
catalysed by the cobalt(II) centres in [CoII4O(bdpb)3]. Their further reaction with
cyclohexene, forming the main product.16,17 ................................................................. 6
Scheme 2 Synthetic scheme for crystallizing green, needle VNU-10. ....................... 27
Scheme 3 Synthetic scheme for crystallizing reddish-yellow, octahedral VNU-15. .. 36
Scheme 4 Synthetic scheme for reddish-yellow, blocked shape crystal of Fe-NH2BDC.
...................................................................................................................................... 47
Scheme 5 Synthetic scheme for reddish-yellow, blocked shape crystal of Fe-BTC. . 52
Scheme 6 Plausible mechanism of direct amination of azoles.123............................... 59
Scheme 7 Amination of Benzoxazole through N-H/CH bonds activation using VNU10 as catalyst. ............................................................................................................... 60
Scheme 8 Initial screening factors for direct oxidative amination of benzoxazole with
piperidine. .................................................................................................................... 63
Scheme 9 Initial factors to investigate the effect of reagent ratio on GC yield of 2(piperidin-1-yl)benzoxazole......................................................................................... 63
Scheme 10 Initial factors to investigate the effect of VNU-10 catalyst molar on GC
yield of 2-(piperidin-1-yl)benzoxazole. ....................................................................... 64
Scheme 11 Initial factors to investigate the effect of reaction solvent on GC yield of 2(piperidin-1-yl)benzoxazole......................................................................................... 65
Scheme 12 Initial factors to investigate the effect of different acids on GC yield of 2(piperidin-1-yl)benzoxazole......................................................................................... 66
Scheme 13 Initial factors to investigate the effect of different oxidants on GC yield of
2-(piperidin-1-yl)benzoxazole. .................................................................................... 68
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Scheme 14 General experimental procedure to 2-(piperidin-1-yl)benzoxazole. ........ 70

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Abbreviation
MOFs

Metal-Organic Frameworks

ZIFs

Zeolitic Imidazolate Frameworks

HFCs

Hydrogen Fuel Cells

PEMFCs

Proton Exchange Membrane Fuel Cells

RH

Relative Humidity

VNU

Vietnam National University

DMA

Dimethyl Ammonium

Ox

Oxalate Anion

DABCO

1,4-diazabicyclo[2.2.2]octane

NH2-H2BDC

Aminoterephthalic Acid

H2NDC

1,6-naphthalene dicarboxylic Acid

H2BDC

1,4-benzene dicarboxylic Acid

H3BTC

Trimesic Acid

DMF

N,N-dimethylformamide

DCM

Dichloromethane

SC-XRD

Single X-ray Diffraction

PXRD

Powder X-ray Diffraction

TGA

Thermal Gravimetric Analysis

FT-IR

Fourier Transform Infrared Spectroscopy
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AAS

Atomic Absorption Spectroscopy

EA

Elemental Analysis

BET

Brunauer-Emmett-Teller

SBU

Secondary Building Unit

GC

Gas Chromatographic

FID

Flame Ionization Detector

GC-MS

Gas Chromatographic-Mass Spectrometry

TBHP

Tert-butyl hydroperoxide

1

Proton Nuclear Magnetic Resonance

H-NMR

13

C-NMR

ICP-MS

Carbon-13 Nuclear Magnetic Resonance
Ion Coupled Plasma-Mass Spectrometry

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INTRODUCTION
Recently, more than 20.000 different metal-organic frameworks (MOFs) have been
reported.1 Several of these were found to have the capabilities to solve modern
challenges. Despite the significant progress in synthesis and applications of MOFs,
there are maintained challenges sought to overcome by novel MOFs, which possess
novel or enhanced properties. For examples:
i. The global demand of cleaner and sustainable energy required the development of
better hydrogen fuel cells (HFCs), which could turn hydrogen into electric power
and release water. However, the low concentration of CO impurity in H2 fuel
stream, which can poison at the Pt catalyst of HFCs, hence the effectively working
condition was identified at medium temperature (T ≥ 100 °C) under low relative
humidity (RH), at which, higher CO tolerance of Pt catalyst was accounted for as
well as reducing the associating cost to maintain high RH at T ≥ 100 °C.
Unfortunately, the current technology, which utilized nafion proton conducting
membrane (the key components within HFCs) could not well support for above
working condition, hence, the quest to synthesize PEMFCs which can
satisfactorily function at medium temperature (T ≥ 100 °C) under low RH was
raised as top urgent goal.2 Recently, MOFs were investigated as proton conducting
membrane in hydrogen fuel cells (PEMFCs), which could achieve the equal
conductivity of nafion although high relative humidity were required, thus,
developing MOFs which can efficiently function at practical working condition of
PEMFCs maintained as significant challenges quested to overcome.3
ii. The demand for highly porous material with uniform and large pore aperture,
which can serve as host scaffold for the catalytic transformation of large organic
substrates, which could not be proceeded by porous material with smaller pore
aperture as well as avoiding the utilization of homogenous catalyst which
consequently contaminated the product. Due to the modular nature of MOFs, its
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pore size can be easily to expanse by employing right combination of metal
clusters and organic linkers, thus opening the approaches to the solution for
accounted challenges.
In our scope of exploration, we employed the cheap and commercial linkers as well
as earth abundant metals such as iron and cobalt to synthesize the novel metal-organic
frameworks. Subsequently, the newly discovered crystal structure were employed as
standpoint for initially justifying the interesting properties of novel MOFs to use in
relevant applications.
In detail, four new metal-organic frameworks have been synthesized and basing on
material architecture, we could able to employ for relevant applications. Among of
these, VNU-15 (VNU=Vietnam National University) was investigated for proton
conductivity with the accounted value, which is higher than nafion, at more practical
working condition of HFCs (low RH and medium temperature).4 Furthermore, the
material, named VNU-10, with large and uniform pore size demonstrated high catalytic
activity over other MOFs, ZIFs with smaller pore size in catalytic transformation of
large organic substrates.5 Applications for other new materials, namely, Fe-NH2-BDC
and Fe-BTC, are still under investigations.

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CHAPTER 1: THE CHEMISTRY & APPLICATIONS OF METALORGANIC FRAMEWORKS
1.1

Definition of Metal Organic Frameworks
Metal organic frameworks (MOFs) is the compound which are consisted of metal

clusters and linker, typically, polytopic organic carboxylates was employed, for
example 1,4-benzenedicarboxylic acid (H2BDC), to construct two-, or threedimensional structures which can be porous (Figure 1).6

Fig. 1 Structure of MOF-5 constructed from Zn4O(CO2)6 cluster and BDC2- linker.6

Fig. 2 Recent progress on synthesizing high surface area material.1

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Recently, more than 20.000 different MOFs have been reported.1 Among these
materials, the highest surface area is 7140 m2 g-1, which far exceeding those of
traditional porous materials such as zeolites and activated carbons (Figure 2).7,8

1.2 Applications of Metal-organic Frameworks
Due to high porosity and the modular nature of MOF design and synthesis, in
which the backbone components [e.g. inorganic and organic secondary building
units (SBUs)], can be easily tailored, MOFs is promised for diverse applications such
as gas storage and separation,9 catalysts,10 proton conduction,3 sensor,11 light harvest,12
drug delivery,13 batteries and supercapacitors,14 and so on.1,15

1.2.1 Applications of Metal-organic Frameworks as Heterogeneous
Catalysis
Catalysts, generally, were classified into homogenous and heterogeneous, in which,
the homogenous catalysts were recognized for fast kinetic and high conversion in
organic synthesis, albeit, several drawbacks have been accounted for, which including
the difficulties to separate the catalysts for recycling investigations as well as desired
products were usually contaminated by catalyst or decomposed products of catalyst. On
the other hand, heterogeneous catalyst was recognized as greener pathway for organic
synthesis owning to its convenience for recycling, in which, the catalysts can be easily
separated from the reaction mixture. Despite significant advantage of heterogeneous
catalysts, organic synthesis employed these catalysts, mostly resulted in low
conversion, hence, one of interesting research direction in the catalytic field has been
devoted to develop more efficiently heterogeneous catalysts.
Traditional heterogeneous catalysts include metal oxides, polymer resin, silica gel
and zeolites, for which, low surface area of metal oxides, polymer resin as well as the
small pore aperture of zeolite, preventing the large organic substrates from reaching
catalytic centers, thus limiting the use for the transformation of large organic substrates.
Another platform, mesoporous silica gel, which possessed large pore and high surface

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area, however, the structure and pore size of the materials are not uniform and the
immobilization of active centers within its pore has maintained challenges.
Oxidative transformation of large organic substrates, commonly required the
formation of active radicals or high oxidation state of the metal centers, which is
unstable with very short decay time, hence required fast diffusion of organic substrate
onto the catalytic active sites. Recently, MOFs have been employed as the platform for
catalytic synthesis of diverse organic compounds.10 In fact, most of published MOFs
possessed the small pore aperture with low surface area (less than 8 Å and 2000 m2 g1

), some of most noticeable MOFs have large internal surface areas and ultralow

densities.7 Due to the large and uniform pore size and definitely coordinative
environment of metal active centers, a few MOFs catalysts exhibited interesting
properties for oxidative transformation of large organic substrates, however, the
examples for these class of catalytic reactions are still very rare.

1.2.1.1 Metal-organic

Frameworks

as

Scaffold

for

Oxidative

Frameworks

for

Oxidative

Transformation of Organic Substrates
1.2.1.1.1 Cobalt-based

Metal-organic

Transformation of Small Organic Substrates
The pyrazolate-based materials, namely, [CoII4O(bdpb)3]n were prepared by
Volkmer in the reactions of H2bdpb and CoCl2·6H2O. The structure of [CoII4O(bdpb)3]n
was deduced to adopt pcu net which is similar to MOF-5 with encloses octahedral
{Co4O(dmpz)6} nodes instead of {Zn4O(CO2)6}. The pore size of the material was
found to be 18.1 Å. [CoII4O(bdpb)3]n has permanent porosity, which was confirmed by
an argon gas sorption experiment. The BET surface areas of [CoII4O(bdpb)3]n were
calculated from the adsorption data to give of 1525 m2 g-1. Similar reaction scheme of
H2bdpb with Co(NO3)2·6H2O leading to the formation of [CoII(bdpb)]n which
constructed from the cobalt rod SBU and bdpb2- in order to form three dimension square
grid framework. [CoII(bdpb)]n possessed 1D channel with the diagonal length of 18.6
Å.16
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Scheme 1 Formation of the observed products through the reaction of tert-butyl peroxy
radicals with cyclohexene. (b) Mechanism for the formation of tert-butylperoxy radicals
catalysed by the cobalt(II) centres in [CoII4O(bdpb)3]. Their further reaction with cyclohexene,
forming the main product.16,17

Liquid-phase oxidation of cyclohexene using TBHP as the oxidant of
[CoII4O(bdpb)3]n and [CoII(bdpb)]n catalysts were investigated. The maximum
cyclohexene conversion after 22 h for [CoII4O(bdpb)3] is 27.5% and 16% for
[CoII(bdpb)]. The main reaction products obtained using both catalysts were tert-butyl2-cyclohexenyl-1-peroxide, followed by 2-cyclohexen-1-one and cyclohexene oxide
(Scheme 1).17
Recently, significant advances have been observed in the cyclohexene oxidation
reaction using cobalt-based MOFs. For example, a novel cobalt-based MOF,
formulated as Co3(OH)2-(tpta)(H2O)4 (tpta = terphenyl-3, 2’’, 5’’, 3’-tetracarboxyate)
has been synthesized. Material characterization revealed that the material could be
dehydrated by heating to transform into dehydrated Co3(OH)2(tpta). Heterogeneous
catalytic experiments on allylic oxidation of cyclohexene show that Co3(OH)2(tpta) has
6 times enhanced catalytic activity than Co3(OH)2-(tpta)(H2O)4, hence coordinatively
unsaturated CoII sites in Co3(OH)2(tpta) have played a significant role in oxidation of
cyclohexene. The maximum conversion for the system was observed around 73.6%.18
Subsequently, similar oxidative transformation of cyclohexene was carried on Ni6


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MOF-74, Co-MOF-74 and the mixed of Co & Ni-MOF-74 by Zhaohui Li et all. The
results revealed that introduction of active Co into the Ni-MOF-74 framework enabled
the inert Ni-MOF-74 to show activity for cyclohexene oxidation with the maximum
conversion of 54.7%. Furthermore, the superior catalytic performance, compared with
pure Co-MOF-74, was observed.19

1.2.1.1.2 Metal-organic Frameworks for Oxidative Conversation of Large
Organic Substrates
Although the oxidative transformation of small organic substrates could be
proceeded by MOFs, it is rare examples for which the oxidative transformation large
organic substrates, except for the couple cases, in which, the MOFs catalyst possessed
large pore size with porphyrin active centers.

Fig. 3 a) Crystal structure of PCN-222; b) Peroxidase-like oxidation reaction of pyrogallol
catalyzed by PCN-222(Fe).20

Recently, Zhou et al published a porphyrin-based MOF, named PCN-222 and took
advantage of large pore size of material with porphyrin active center to use for catalyst.
The self-assembly of tetrakis(4-carboxyphenyl)porphyrin) and zirconium cluster
leaded to csq framework, in which, the architecture contained hexagonal and triangular
one dimension channels with diameter of 36 and 8 Å (Figure 3a). The iron analogue
7


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