Mesoporous Materials Presentation Overview

Mesoporous Materials
Presented by Mannu Kaur
M.Tech NST 1st year (2nd sem)
00740801015

Outline
 What are Porous materials?
Classification of Porous materials
What is Mesoporous material?
Synthesis of Mesoporous material
Applications
Magnetic Nanoparticles with Mesoporous Structures
5/5/2016 Mannu Kaur 2

Zeolites
• Zeolites are porous, hydrated aluminosilicates. They may be natural minerals or
synthetic materials.
• The general chemical composition of a zeolite is:
Mx/nSi1-xAlxO2 · yH2O
Where M = e.g. Na+, K+, Li+, Ag+, NH4
+, H+, Ca2+, Ba2+
• These are three dimensional structure built from tetrahedra. Some silicon atoms have
been replaced by aluminium.

Background
• The synthesis of porous material started in late 1940’s with synthesis
of synthetic Zeolites by Barrer, Breck, Milton and Co-workers.
• Coming years witnessed the formation various zeolites with different
compositions and topologies.
• In 1982 Flenigen reported the formation of non-silicate microporous
materials- formation of Aluminophosphate sieves.
• In 1992 Mobil scientists synthesized porous material, M41S, that had
pore size in meso range.

What are Porous materials
 It can be defined as, continuous, solid material filled with voids
Porous materials are characterized by its ‘Porosity’.
There are a variety of porous materials differing in chemical
composition, pore geometry and size.

Porosity
Porous material contain pores (cavities, channels) which are deeper
than they are wide.
Either describe the pores, or describe the cell/pore walls
Accessibility:
a: closed pores
b,c,d,e,f: open pores
b, f: blind pores (dead-end )
e: through pores
Shape:
c:Cylindrical open
f:Cylindrical blind
b: ink-bottle-shaped
d: funnel shaped
g: roughness

Pore size
Pore size is important for applications. IUPAC, three pore size regimes.
•Microporous, smaller than 2 nm
•Mesoporous, between 2 and 50 nm
•Macroporous, larger than 50 nm
Different pore size material show characteristic physical
adsorption isotherm.
Microporous: these material show type-I isotherm
Mesoporous: type-IV isotherm is seen in this material
Associated with capillary condensation
Macroporous: this material shows type-II adsorption isotherm

Classification of Porous material

Mesoporous materials
 Mesoporous materials are the materials which have their pore size in
between Micro- and Macroporous materials.
They can be used in variety of applications mainly because of its high
- surface area
- pore volume
- stability
The most common method of synthesis of mesoporous material is, Soft
template method.

Synthesis of Mesoporous materials
Soft template Hard template
• Uses soft template like
organic molecules.
• Good shape, size and
morphology
• SBA-15, MCM-41 etc.
• Uses inorganic material
like silica.
• Difficult work up, hard
to get good morphology
• CMK-1

Hard template
Synthesis of mesoporous carbons with well-defined mesoporous
structure is usually done by hard template method
a) Preparation of silica gel with controlled pore structure.
b) Impregnation/infiltration of the silica template with monomer or
polymer precursors.
c) Cross-linking and carbonization of the organic precursors.
d) Dissolution of the silica template.

Preparation of silica gel
• Pluronic P123 (block co-polymer), dissolved in distilled water, in
presence of acid.
• After complete dissolution, n-butanol is added and continued to stir for
1h. Followed by addition of tetraethyl orthosilicate (TEOS).
• The mixture was further kept for stirring and subsequently
hydrothermally heated.
• Removal of surfactant by extraction with water followed by
calcination.

Soft template method for synthesis
1. Surfactants.
2. Formation of Micelles.
3. Inorganic precursor .
4. Interaction of Micelles with inorganic precursor.
5. Hydrothermal treatment followed by separation and drying
6. Removal of template.
7. Proposed mechanism

1. Surfactant/ Template
 Large organic molecules(High molecular weight) with both
hydrophilic and hydrophobic groups.
 Depending upon charge they can be
classified as
Cationic Anionic Non ionic/neutral
•Excellent solubility
•High critical Micelle con.
•toxic and expensive
• repulsion between the
anionic surfactant is more.
•High critical micelle temp.
•non-toxic and cheap

2. Formation of micelle
 At a Low surfactant concentration will favor arrangement
on the surface.
 As the concentration increases surface being more
crowded as result molecule arrange in to micelles.
 At certain concentration the surface is completely loaded
and any further addition leads to the Micelle
arrengment.This conc. is known as CMC.
 Beyond the CMC self assembly of micelle occurs to from
3D and 2D rod like arrays.
 Different template have the different CMC.

3.Inorganic precursor and pH
Inorganic Precursor silica depends upon pH
Basic synthesis (pH =9.5 to 12.5)
-Anion species is obtained
Acidic synthesis(pH= 1 to 2 )
-Cationic species is obtained

4. Interaction of Micelles with inorganic
precursor
 Direct interaction of Surfactant with inorganic precursor
Basic -Medium Acidic-Medium

Interaction of non ionic Surfactant with inorganic precursor through
intermediate ions.

5. Hydrothermal treatment followed by separation
and drying.
 80 -150 °C is temperature is usually used.
 High temperature will lead to the decomposition of surfactants.
 Separation – filtration or centrifugation.
 Washing –alcohol or water. Basic media needs through washing.
 Drying at room temperature is good.

6. Removal of template.
 Removal of template will give rise to mesoporosity
Different ways by which template can be
removed
Calcination
•Slow heating rate.
•No surfactant recover
•Not good for low thermal
stable materials
•CTAB -350 °C
Solvent Extraction
• Solvent ethanol /THF
• small HCl is added
• Surfactant can be
reused

Effect of surfactant
1. Critical micelle concentration
Low micelle conc. are good to get ordered materials.
2. Packing parameter (g)
g = V / ao
V=Total volume of surfactant hydrophobic chains
ao= Effective hydrophilic head group area at the aq. micelle surface.
g <1/3 = cubic and 3 D hexagonal,
1/3<g>1/2 = 2D hexagonal
1/2<g>2/3 = cubic
g=1 = Lamellar
3.The hydrophilic and hydrophobic Volume ratio (VH /VL)

Different type of surfactant arrangement

Complete synthesis summary

Functionalization of Mesoporous
material
• Mesoporous silicates have very high surface area and their surfaces are
covered by silanol groups, which makes the functionalization of the
pore surface of the mesoporous materials adjustable.
• The surface functionalization of mesoporous silicates could change the
chemical and physical properties of these materials dramatically.
• There are two major ways to functionalize the surface of mesoporous
silicates by organic functional groups, named as post-synthesis
grafting and co-condensation.

Grafting method
• It is a post-synthesis method to modify a pre-fabricated inorganic
mesoporous material surface, by attachment of functional groups to
the surface of material, usually after surfactant removal.
• In the process of grafting mesoporous silicates, the surface silanol
groups (Si-OH), which can be present in high concentration, act as
convenient anchoring points for organic functionalization.

Co-condensation Method
Co-condensation method is another strategy to functionalize
mesoporous silicate’s, surface by sol-gel chemistry between
tetraalkoxysilane and one or more organoalkoxysilanes with Si-C bonds.

Characterization of Mesoporous material
Powder XRD pattern for ordered
mesoporous silica templates and
ordered mesoporous carbon
TEM image of CMK-1

Template synthesis of nanowires in O/I
hybrid Mesoporous material
• The “ship-in-bottle” synthesis is one of the promising methods for template synthesis of
metal complexes and nanocomposites mesoporous materials.
• Organic-inorganic hybrid HMM and other hybrid materials have mesopores to
accommodate bulky metal complexes or nanocomposites, which are accessible to large
substrates in catalytic reactions.
• HMM-1 dried under vacuum. The dry HMM-1 was impregnated with an aqueous solution
of H2PtCl6 .6H2O and RhCl3.3H2O.
• Then the sample was irradiated with a high-pressure mercury lamp. The resulting pale
gray powder, designated Pt-Rh/HMM-1. Pt-Pd/HMM-1 (Pt/Pd ) the same method with
H2PtCl6 .6H2O and H2PdCl4 as precursors.

Drug Delivery
• The functionalization of MCM-41 and
SBA-15, respectively, with amino groups as
an effective method to control IBU release.
• The ionic interaction between the
carboxy groups in IBU and the amino groups
on the matrix surface allows the release rate of
IBU from amino functionalized SMMs to be
effectively controlled (SMM=silica
mesoporous material).
• NMR analysis revealed that IBU molecules
are tightly linked at the surface because the
drug–surface ionic interactions are stronger
than the IBU dimer hydrogen bonds

Magnetic nanocomposites with
Mesoporous structures
Magnetic nanoparticles have potential applications in magnetic fluids,
catalysis, biomedicine, magnetic resonance imaging, data storage and
environmental remediation.
There are many problems that are associated with Magnetic
nanoparticles, such as instability over long periods due to their
tendency to aggregate.
As a solution, these magnetic nanoparticles can be coated with
suitable mesoporous material, in order to exploit their properties and
keep them stable.
Mesoporous materials with their attractive properties makes them
suitable to be used as drug delivery carriers, imaging agents, water
treatment adsorbents and as catalysts.

Types of magnetic mesoporous
materials
Magnetic mseoporous nanocomposites with different morphologies,
structures and particle size can be broadly classified into:
A. Monodisperse
magnetic np
embedded in
mesoporous
nanospheres
B. Microspheres
encapsulating magnetic
cores into
perpendicularly aligned
mesoporous shells
C. Ordered
mesoporous materials
Loaded with magnetic
np inside porous
channels
D. Rattle type
magnetic
nanocomposites.

Synthesis of magnetic nanoparticles

Magnetic NPs inside the porous channels
• Selecting monodisperse mesoporous silica as hosts,
ferrocenecarbaldehyde as the iron precursor and furfuryl alcohol as a
solvent, a large amount of γ –Fe2O3 NPs can be incorporated into the
silica host.
• Magnetic iron metal/silica and magnetic/silica nanocomposites have
been prepared via temperature-programmed reduction of an iron oxide
on SBA-15.
• The resulting Fe3O4 /SBA-15 and Fe/SBA-15 exhibit
superparamagnetic properties.

Biomedical and biotechnological
applications
These materials are attractive magnetic probes for biological imaging
and therapeutic applications.
Core diameter near about 20nm and overall particle diameter near
about 50nm, the size is much smaller than size of the cell and is
comparable to size of nuclei.
When these are coupled with target agent, they serve as nanovectors
and interact specifically with biomolecules.
Drug carriers with magnetic NPs can respond to an external magnetic
field, which makes them good magnetic targeting agents for drug
delivery.

Wastewater treatment
Removal of toxic heavy metal ions from wastewater is a challenge.
Various organo-functionalized mesoporous materials such as thiols,
thioether and amino groups have been reported for metal ion removal
and dye adsorption.
These functionalized materials can be easily separated from aqueous
systems by an external magnetic field and lower operational costs in
adsorbent separation.
Shi and coworkers synthesized thioether functionalized mesoporous
aluminosilicate hollow spheres with magnetic cores.
These materials exhibited highly selective adsorption of Hg+2 .

Catalysis
Magnetic separation provides a easy method for removing and
recycling magnetized species.
This approach could be used to prevent the agglomeration of catalyst
particles during recovery.
Various types of reactions are catalyzed using magnetic mesoporous
nanocomposites, such as olefin epoxidation, hydrogenation,
Knoevenagel reaction.

References A Review: Fundamental Aspects of Silicate Mesoporous Materials Zeid A. ALOthman
 Magnetic Nanocomposites with Mesoporous Structures: Synthesis and Applications, Jian Liu, Shi Zhang Qiao, Qiu Hong Hu and Gao Qing
Lu
 Soft templating strategies for the synthesis of mesoporous materials: Inorganic, organic–inorganic hybrid and purely organic solids
 On the Controllable Soft-Templating Approach to Mesoporous Silicates,Ying Wan and Dongyuan Zhao, chemical reviews, Volume 107,
Number 7
 Ordered porous materials for emerging applications Mark E. Davis
 Porous Materials Metal-Organic Frameworks 2012 Nanocamp NCMN, UNL Dr. Jian Zhang & Jacob Johnson Department of Chemistry
 Soft templating Davos Marine, Quibus Laurent, Pecher Romain, Schrobiltgen Jordan.
 Porous Inorganic Materials Xiqing Wang, Xianhui Bu & Pingyun Feng California State University, Long Beach, CA, USA, University of
California Riverside, Riverside, CA, USA
 Mesoporous Materials for Drug Delivery Mara Vallet-Reg,Francisco Balas, and Daniel Arcos
 A Review: Fundamental Aspects of Silicate Mesoporous Materials Zeid A. AL Othman
 Synthesis, Characterization, and Catalytic Properties of a Microporous/Mesoporous Material, MMM-1 Raja H. P. R. Poladi and Christopher
C. Landry
 Syntheses of High-Quality Mesoporous Materials Directed by Blends of Nonionic Amphiphiles under Nonaqueous Conditions Bozhi Tian,
Xiaoying Liu, Zhendong Zhang, Bo Tu, and Dongyuan Zhao
 Porous Inorganic Materials Xiqing Wang, Xianhui Bu & Pingyun Feng
 Functionalization of mesoporous silica nanoparticles and their applications in organo-, metallic and organometallic catalysis Yulin Huang

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