Ph'D' seminar I

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Mesoporous Materials an Architectural
Opportunity
Ph.D. seminar I 05-02-08
Dept. of Chemistry IIT Madras
Kuppan B CY06D022
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Overview
Introduction Mesoporous materials Merits and
demerits Synthesis and characterization of M41s
and SBA-15 Pore size control Applications of
mesoporous silicates Mesoporous carbon Synthesis
and characterization of mesoporous
carbons Applications Electrochemical activity
Transition metal oxides Hydrogen storage
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Introduction
Porous materials
eg ZSM-5,AlPO
MCM-48,SBA-15,CMK-n photonic
crystals P.D lt 2 nm
2-50 nm
gt 50 nm SA
300-500 m2g-1 1000-3000
m2g-1 10-500 m2g-1

• Porous solids - scientific and technological
  interest - ability to interact with atoms, ions
  and molecules at surfaces and throughout bulk of
  material
• Distribution of sizes, shapes and volumes of the
  void spaces in porous materials directly related
  to their ability to perform desired function in
  particular application.
• High SA/volume ratio provides a strong
  driving force to speed up thermodynamic processes
  
• that minimize free energy
• In high surface area materials the active
  sites are more isolated
• Materials with uniform pores - separate
  molecules on basis of size.
• Used as adsorbents, catalyst supports, and
  electrode materials.

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Overview of silica based mesoporous materials
P. Selvam, S. K. Bhatia and C. S. Sonwane, Ind.
Eng. Chem. Res., 40 (2001) 3237
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Features of silica based mesoporous family

• High internal surface area (600-1500 m2g-1)
• Large number of internal surface hydroxyl groups
• Hydrophobic and hydrophilic nature

Merits of SBA-15
Demerits of M41S family

• Thin wall (0.3-1.0 nm)
• Hydrothermal stability

• Hydrothermal stability
• Thermal stability (1000C)
• Tunable uniform pore size (5-30 nm)
• Wall thickness (3-7 nm)
• Channels are inter connected

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Schematic representation
Silica/surfactant 1/0.27
calcination
As-synthesized MCM-41 (hexagonal structure)
MCM-41
Silica/surfactant 1/0.60
calcination
MCM-48
As-synthesized MCM-48 (cubic structure)
J. S. Beck, J.C. Vartuli, W. J. Roth, M. E.
Leonowiez, C. T. kresge, K. D. Schmitt, C. Chu,
D. H. Oison, and E. W. Sheppard. S. B. McCullen,
J.L. Schlenker. J. Am. Chem. Soc., 114 (1992)
10834
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Synthesis and characterization of MCM-41
1.55gTMAOH 15ml H2O 4 g f.silica
6.56 g CTAB 0.7g NaOH 57ml H2O
Stirred 10 min
Stirred 30 min
Soln.y
Soln.x
TEM
Soln.x Soln.y Stirred 1.5 h
XRD
pH 11.2-11.5
N2 isotherm
Autoclave 100 ºC 1 day
Cal. 550 ºC
C.T. Kresge, M. E. Leonowicz, W. J. Roth, J. C.
Vartuli and J. S. Beck, Nature, 359 (1992) 710
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Synthesis and characterization of MCM-48
0.8 g NaOH 18.2 ml H2O 8.33 g TEOS
8.74 g CTAB 25 ml H2O
Stirred 20 min
Stirred 10 min
Soln.X
Soln.Y
XRD
Soln.X Soln.Y Stirred 1.5 h
N2 isotherm
pH 11.2-11.5
TEM
Autoclave at 100 ºC 3 days
Cal at 550 ºC
J. S. Beck, J.C. Vartuli, W. J. Roth, M. E.
Leonowiez, C. T. kresge, K. D. Schmitt, C. Chu,
D. H. Oison, and E. W. Sheppard. S. B. McCullen,
J.L. Schlenker. J. Am. Chem. Soc., 114 (1992)
10834
9
Synthesis and characterization of SBA-15
TEM
XRD
4g P123 22 ml H2O 38 ml HCl (2M)
Stirred 350C 1 h
7 g TEOS
Stirred 350C 24 h
N2 isotherm
Aged at 100 0C 48 h
Washed EtOH and dried Calcined 550 0C 6 h
SBA-15
SBA-15
D.Zhao, J. Feng, Q. Huo, N. Melosh, G. H.
Fredrickson B. F. Chmelka and G. D. Stucky,
Science, 279 (1998) 548
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Control of pore diameter in mesoporous silicates
Length of surfactant alkyl chain
20Å
Surfactant Micelle C12
40Å
1.5 nm
Addition of solubilization agents
Hydrophobic

Micelle
Interior
Auxiliary
Organic
CH
CH
3
3
CH
CH
CH
3
3
3

Hydrophilic
CH
Exterior

3
Mesitylene
Swelled
Micelle
C.T. Kresge, M. E. Leonowicz, W. J. Roth, J. C.
Vartuli and J. S. Beck, Nature, 359 (1992) 710
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Applications of mesoporous silicates
Structure/Property Control

• Modification of surface/framework of mesoporous
  silicates for various applications
• Grafting/anchoring eg amine, acids
• Ion-exchange eg CrO22, VO2 UO22
• Solid acid Al3,Ga3
• Redox eg Fe, Ti, Cr.
• Explore confinement properties (formation of
  nanoparticles)
• Use as mould (template for Ordered Mesoporous
  Carbon)

Vary the Pore Size 1.5 nm to 25 nm
Vary the Chemical Composition
Anchor Metals and Catalysts
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CARBON
allotropes

• Hard (diamond) and soft material (graphite)
• Carbon is capable of forming multiple stable
• covalent bonds
• Covalent character retention
• Variable hybridization possible
• Dimensionality 1-3 D is possible
• Carbon can have the surface area from few
• m2g-1 to 3000 m2g-1.
• Capable of sustaining linear, triangular and
• tetrahedral configurations
• Coordination number is variable/expandable

a
c
b
f
d
e
g
h
a. Diamond, b.graphite, c. lonsdaleite, d-f.
buckyballs, g. amorphous carbon, h. carbon
nanotube
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Why mesoporous carbon?

• in microporous carbon the pore size is not
  uniformly distributed
• Pore volume is smaller
• Metal dispersion- not uniform tend to Oswald
  ripening
• In carbon nanotubes(CNTs) the tube diameters
  difficult to control
• CNTs are obtained as a powder, with separate
  or entangled nanotubes that
• exhibit a broad distribution in tube
  diameters.
• Single walled carbon nanotubes (SWNTs) undergo
  self organization to a bundle.
• CNTs system do not have rigid
  structural periodicity

Advantages of mesoporous carbon

• High surface area (up to 3000 m2g-1)
• Uniform pore size
• Large pore volumes
• High Periodicity
• channels - individual nano scale reactors

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Overview of mesoporous carbons
15
Mesoporous carbon (CMK-1)
xMCM-48 sucrose/furfuryl alcohol H2SO4
H2O
Dried 100 0C 6 h and 160 0C 6 h
Black powder
sucrose/FFA H2SO4 H2O
Dried 100 0C 6 h and 160 0C 6 h
Carbonized 900 0C 6 h N2 atm.
Washed 5 HF and EtOH
CMK-1
x Si or Al/Fe
R. Ryoo, S. Hoon and S. Jun, J. Phys. Chem. B,
103 (1999) 7743
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Schematic representation CMK-1
sucrose/FFA
polymerization
xMCM-48
pyrolysis
HF etching
carbon/XMCM-48 composite
CMK-1
J. Lee, J. Kim, and T. Hyeon, Adv. Mater, 18
(2006) 18
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Characterization of CMk-1
TEM of CMK-1
XRD
110
210
220
CMK-1
N2 isotherm of CMK-1
MCM-48
R. Ryoo, S. Hoon and S. Jun, J. Phys. Chem. B,
103 (1999) 7743
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Mesoporous carbon (CMK-3)
SBA-15 sucrose/furfuryl alcohol H2SO4 H2O
Dried 100 0C 6 h and 160 0C 6 h
Black powder
sucrose/FFA H2SO4 H2O
Dried 100 0C 6 h and 160 0C 6 h
Carbonized 900 0C 6 h N2 atm.
Washed 5 HF and EtOH
CMK-3
S. Jun, S. H. Joo, R. Ryoo, M. Kruk, M. Jaronice,
Z. Liu, T. Ohsuna and O. Terasaki, J. Am. Chem.
Soc, 122 (2000) 10712
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TEM of CMK-3
Characterization of CMk-3
XRD
N2 isotherm of CMK-3
P/P0
S. Jun, S. H. Joo, R. Ryoo, M. Kruk, M. Jaronice,
Z. Liu, T. Ohsuna and O. Terasaki, J. Am. Chem.
Soc, 122 (2000) 10712
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Textural properties
Sample SBET (m2g-1) pore vol.
(cm3g-1) pore size (nm)
MCM-48 1000-1500 0.5 -1.5
2.0-5.0 CMK-1 1500-2000
0.5-2.0 3.0-6.0 SBA-15
850- 1000 0.8- 1.3
4.0-20.0 CMK-3 1200-1800
0.5-1.9 5.0-15.0
S. Jun, S. H. Joo, R. Ryoo, M. Kruk, M. Jaronice,
Z. Liu, T. Ohsuna and O. Terasaki, J. Am. Chem.
Soc, 122 (2000) 10712
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Synthesis of FDU-17
0.3 g PPO-PEO-PPO 5 g EtOH
Stirred 1 h
5 g resol precursor
Stirred 10 mins
Gel poured into dish
evaporate EtOH at RT 5-8 h
Heated at 100-160 C for 24 h
cal at 450 C 4 h
Carbonization at 600-1000 C
FDU-17
Y. Huang, H. Cai, T. Yu, F. Zhang, F. Zhang, Y.
Meng, D. Gu, Y. Wan, X. Sun, B. Tu, and D. Zhao,
Angew. Chem. Int. Ed., 46 (2007) 1089
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Schematic representation FDU-17
Y. Huang, H. Cai, T. Yu, F. Zhang, F. Zhang, Y.
Meng, D. Gu, Y. Wan, X. Sun, B. Tu, and D. Zhao,
Angew. Chem. Int. Ed., 46 (2007) 1089
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SAXS spectra
TEM of FDU-17
110
100
211
111
Y. Huang, H. Cai, T. Yu, F. Zhang, F. Zhang, Y.
Meng, D. Gu, Y. Wan, X. Sun, B. Tu, and D. Zhao,
Angew. Chem. Int. Ed., 46 (2007) 1089
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Pore size distribution
N2 isotherm
1000C
800C
1000C
800C
600C
450C
600C
450C
Y. Huang, H. Cai, T. Yu, F. Zhang, F. Zhang, Y.
Meng, D. Gu, Y. Wan, X. Sun, B. Tu, and D. Zhao,
Angew. Chem. Int. Ed., 46 (2007) 1089
25
Textural properties of FDU-17
Sample d111 (nm) a0 (nm)
SBET (m2g-1) pore size (nm)
pore vol. (cm3g-1)
FDU-17-350 22.1 38.3
- -
- FDU-17-450 20.1 34.8
510 4.0-6.9 0.33
FDU-17-600 18.8 32.6
590 3.2-5.4
0.35 FDU-17-800 18.8 32.6
780 3.5-5.8
0.47 FDU-17-1000 18.8
32.6 870 3.9-5.9
0.54
Y. Huang, H. Cai, T. Yu, F. Zhang, F. Zhang, Y.
Meng, D. Gu, Y. Wan, X. Sun, B. Tu, and D. Zhao,
Angew. Chem. Int. Ed., 46 (2007) 1089
26
Applications of mesoporous carbon

• Electrochemical catalytic activity
• ordered mesoporous transition metal oxide (CuO)
• Silica templates active and inactive sites
• carbon sites are all equal (residual
  valency of carbon are same in all directions )
• carbon topographically same in all
  directions
• Hydrogen storage
• adsorption ability
• high specific surface area and pore
  volume
• low mass density

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Electrochemical catalytic activity
High metal dispersion saves expensive metals,
controlling structure sensitivity Selectivity
can be changed by decreasing cluster size
XRD CMK-3
Preparation of Pt cluster on CMK-3/CB
CMK-3/CB acetone H2PtCl6
stirred
Dried 60C
Heated H2 300 C 2h
TEM CMK-3
Outgassed 2h
H2 chemisorption
Pt-Pt coordination no. 5.4 1.5 H atoms per Pt
atom 50 wt Pt Pt cluster shows narrow
particle size distribution (2.5 nm) Activated
carbon fiber, carbon block Pt cluster shows
wide pore size distribuion (30 nm)
S. H. Joo, S. J. Choi, I. Oh, J. Kwak, Z. Liu, O.
Terasaki and R. Ryoo, Nature, 414 (2001) 470.
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TEM images
Pt/CMK-3
Pt/CMK-3
5 nm
60 nm
Pt/Carbon black
Pt loading
60 nm
S. H. Joo, S. J. Choi, I. Oh, J. Kwak, Z. Liu, O.
Terasaki and R. Ryoo, Nature, 414 (2001) 470.
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Catalytic activity
Preparation of electrodes and electrochemical
activity
Pt/CMk-3 or Pt/CB EtOH Nafion
Ultrasonication
30 µl ink on electrode
Dried 70 C
10,000 r.p.m in 0.1M HClO4 sat. O2
Catalytic activity in A per g of Pt measured at
potential of 0.9V w.r.t NHE and at rotating
speed 10,000 r.p.m in 0.1 M HClO4 with O2

• The catalytic current of the Pt OMCs electrode
  began to raise much more sharply at a more
  positive potential, which directly improved the
  cell efficiency.
• uniformity and the decrease in the Pt cluster
  size when Pt is supported on the OMCs.
• This properties may also be useful for the
  construction of fuel cell anodes that operate
  with direct methanol oxidation.

S. H. Joo, S. J. Choi, I. Oh, J. Kwak, Z. Liu, O.
Terasaki and R. Ryoo, Nature, 414 (2001) 470.
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Mesoporous CuO
2 g CMK-3 20 ml of 0.4M Cu(NO3)2
stirred 2 h 100 0C
MTMOs- catalysis, biological separation, photonic
and electronic devices, and drug
delivery. direct decomposition N2O to N2, CO
oxidation and the complete combustion of the
HCs. CuO seems to be the better
catalyst. Meso.CuO with an ordered mesoporous
structure, large surface area and crystalline
walls are expected to provide enhanced catalytic
performance Electrode material in Li-ion
batteries
Dried vaccum
Black powder
Heated 300 0C N2
Repeated twice
Cal. 500 C 48 h in air
Meso.CuO
X. Lai, X. Li, W. Geng, J. Tu, J. Li, and S. Qiu,
Angew. Chem. Int. Ed., 46 (2007) 738
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Characterization of meso CuO
N2 isotherm CuO
XRD
CuO
Meso.CuO
CMK-3
SBA-15
TEM CuO
001
110
X. Lai, X. Li, W. Geng, J. Tu, J. Li, and S. Qiu,
Angew. Chem. Int. Ed., 46 (2007) 738
32
Physical properties of SBA-15, CMK-3 and meso.CuO
Sample lattice parameter (nm) SBET (m2g-1)
pore size (nm) pore vol. (cm3g-1)
wall thickness (nm)
SBA-15 10.51 592
6.24 0.89
4.27 CMK-3 9.35
927 4.15
0.89 - CuO 9.18
149 5.46
0.54 3.72

• decrease in a0 thermal treatment
• Pore size of CMK-3 similar to SBA-15 and meso
  CuO wall thicknesses
• Perfect replication from SBA-15 to
  CMK-3 and CMK-3 to meso CuO
• Surface area difference of SBA-15 to meso CuO
• (bulk densities CuO 6.49
  gcm-3 and SiO2 -2.26 gcm-3)

X. Lai, X. Li, W. Geng, J. Tu, J. Li, and S. Qiu,
Angew. Chem. Int. Ed., 46 (2007) 738
33
XRD
Hydrogen storage

• Hydrogen clean fuel
• Difficulty storage and transport
• DOE set 6.5 wt
• Carbon material having uniform micropore
• size can be better storage medium.
• The chemical activation of OMCs with KOH
• uniform and higher microporosity

CMk-8 KOH
TEM
Heated 900 ºC N2
KOH/ CMK-8 0 - 5
Washed 3 times 3 M HCl dist. H2O
An-CMK-8
M. Choi, and R. Ryoo, J. Mater. Chem., 17 (2007)
4204
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Ar adsorption
Pore textural properties
Change in Textural properties
M. Choi, and R. Ryoo, J. Mater. Chem., 17 (2007)
4204
35
H2 adsorption Vs BET SA
H2 adsorption Vs micropore.vol
H2 adsorption isotherm
M. Choi, and R. Ryoo, J. Mater. Chem., 17 (2007)
4204
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