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Mesoporous materials
The document discusses mesoporous materials, detailing their synthesis through soft template strategies and their applications in various fields such as catalysis, environmental science, and biomedical engineering. Mesoporous materials have specific characteristics like large surface area, high stability, and are useful as drug delivery systems and in bone tissue engineering. The paper also compares zeolites and mesoporous materials, highlighting differences in properties and synthesis methods.
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Introduction to mesoporous materials and the outline of their synthesis and applications.
Introduction to porous materials including their definition, history with zeolites and classification by pore size.
Mesoporous materials properties, such as surface area (400-1000 m2/g), stability, and a comparison with zeolites.
Two synthesis methods: soft and hard templates, focusing on soft templates like organic molecules.
Formation of micelles from surfactants, critical micelle concentration, and factors affecting surfactant arrangements.
Interaction mechanisms of surfactants and inorganic precursors, including different pH conditions.
Processing steps for improving material regularity and methods for template removal to achieve mesoporosity.
Different synthesis mechanisms; including silicate rod assembly and self-assembly processes of surfactants.
Methods for characterizing mesoporous materials, including XRD, N2 sorption, and TEM techniques.
Diverse applications of mesoporous materials: catalysis, environmental applications, drug delivery, and tissue engineering.
Contributors to the field of mesoporous materials including their discoveries and innovations.
References cited in the presentation providing foundational literature on mesoporous materials.
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Mesoporous materials
- 1. Mesoporous Materials –Synthesis and Applications Vijaykumar S.Marakatti, PPISR, Bangalore.
- 2. Outline of thetalk Introduction to porous materials Classification of porous materials Synthesis mechanism of mesoporous materials Applications of mesoporous materials
- 3. Introduction “the overwhelming tendencyfor solids to minimize void space within their structure” is inherent , porous materials are difficult to make naturally. But Einstein say “ in the middle of difficulty lies opportunity” The above statement was made true by the Mobil scientist in the year of 1992 by successfully synthesizing the Mesoporous materials (MCM-41 and MCM-48) by using soft template strategy. This opened a new area of materials called Mesoporous materials, and still lot of work are fascinating in this field.
- 4. What are Porousmaterials Most generalized definition of porous materials is continuous and solid network material filled through voids. A material can be recognized as porous if its internal voids can be filled with gases. The history of porous materials began with the zeolites having aluminoisilicates framework which was synthesized by the use single template molecule with small pore.
- 5. Classification of porousmaterials Depending on pore size Depending on building framework Micropoorus Mesoporous Macroporous <2nm 2-50 nm >50nm ZSM-5 MCM-41 Sponge Purely inorganic Organic Inorganic Purely hybrid organic Silica MOF organic porous polymers
- 6. Mesoporus Materials Mesoa Greek prefix – “ in between ” - micro and macro porous system Mesoporous materials may be ordered or disordered. They possess high Surface area -400 -1000 m2/g Large pore volume High stability -500 -600 °C They are usually synthesized by the use of Soft template method. Ex: MCM-41,SBA-15,FDU-11,IITM-56 etc.
- 7. Difference between thezeolites and mesoporous materials Zeolites Mesoporous Materials Highly crystalline Periodic arrangement with amorphous in nature TO4 networks TO4,TO5 and TO6 networks Si and Al are four connected by covalent Si and Al are 2 or three connected ,more bond, less surface hydroxyl groups surface hydroxyl groups Hydrophobic surface area Hydrophilic surface area High hydrothermal stability Less hydrothermal stability Crystalline walls and are thick Amorphous walls and are thin Synthesis temp is high (80 – 300 °C) Synthesis temp is low (-10 to 120°C) Long crystallization time Formation rates are fast Aqueous media is required for Non –aqueous solvents and non polar crystallization solvents can be used Synthesis of zeolite is carried out in Synthesis pH rang is from 0 to 12 neutral /weakly acid media
- 8. Synthesis of mesoporousmaterials Soft template (endo template) Hard template (exo template, nano casting) • Uses soft templates like organic •Uses inorganic materials like silica, carbon etc molecules . •Tedious work up, hard to get good morphology and costly •Good shape , Size and morphology. CMK-1 simple • SBA-15 ,MCM-41 etc Meso-silica CMK-1
- 9. Synthesis of mesoporousmaterials using soft template strategy 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 8. Characterization of material.
- 10. 1. Surfactant/ Template/Structuredirecting agent. 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 •Excellent solubility •Excellent solubility •High critical Micelle con. • repulsion between the • High critical micelle temp. •acidic and basic media anionic surfactant is more. •Acidic / basic media • toxic and expensive • non-toxic and cheap
- 11. 2. Formation ofmicelle • 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. • To get ordered materials – 0 to20 mg/L
- 12. Different type ofsurfactant arrangement
- 13. What Makes themto show different type of arrangements ? 1. Critical micelle concentration Low micelle conc. are good to get ordered materials. 2. Packing parameter (g) g = V / ao l V=Total volume of surfactant hydrophobic chains+ co-solvnet. ao= Effective hydrophilic head group area at the aq. micelle surface. l = kinetic surfactant tail length. 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)
- 14. 3.Inorganic precursor andpH Inorganic Precursor silica depends upon pH Basic synthesis (pH =9.5 to 12.5) -Polymerization and cross Linkage of silicate species are reversible Silica gel, colloidal sol, Water glass , TEOS etc. Acidic synthesis(pH= 1 to 2 ) - Irreversible. - Slow hydrolysis TEOS is preferred.
- 15. 4. Interaction ofMicelles with inorganic precursor. Direct interaction of Surfactant with inorganic precursor Basic -Medium Acidic-Medium
- 16. Interaction of Surfactantwith inorganic precursor through intermediate ions Acidic-Medium Basic -Medium
- 17. Interaction of nonionic Surfactant with inorganic precursor through intermediate ions. Hydrogen bonds favors most of times
- 18. 5. Hydrothermal treatmentfollowed by separation and drying. Method to improve mesoscopic regularity's of products. Reorganization, growth and crystallization 80 -150 °C is temperature is usually used. High temperature will lead to the disorder and decomposition of surfactants. Separation – filtration or centrifugation. Washing –alcohol or water. Basic media needs through washing. Drying at room temperature is good.
- 19. 6. Removal oftemplate. Removal of template will give rise to mesoporosity Different ways by which template can be removed Light irradiation Calcination •Slow heating rate. Solvent Extraction • Microwave • N2 -1 hr • Solvent ethanol /THF •Ultraviolet rays O2- 4-6 hr – 2 °C/min • small HCl is added O3 and O • O2-1 °C/min • Surfactant can be reused • No surfactant recover • low Surface silanol groups • Not good for low thermal stable materials •P-123 -550 °C • CTAB -350 °C
- 20. p6mm Ia3d, SBA-15 MCM-48 Pm3n SBA-1 and 6 Fd3m Im3m SBA-16 Fm3m. FDU-2 KIT-5
- 21. Proposed mechanisms forsynthesis mesoporous materials 1. Silicate rod assembly 2 or 3 monolayer's of silicates species first deposits on isolated surfactant miceller rods
- 22. 2. Cooperative selfassembly Low concentration Surfactant
- 23. 3. True liquidcrystal templating route High concentration Surfactant
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- 25. 7. Characterization ofmesoporous materials 1. Low angel XRD 0.5 -5 -2theta - orederness / disorder. 2. N2 sorption measurements –BJH method Surface area/pore diameter /pore volume 3. TEM images Order ,Morphohology , Wall thickness
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- 27. Application Chemical Catalysis 1.Mesoporous Materials as catalyst Al-MCM-41 ,B-MCM-41, Sn-SBA-15 - Acidic K- AlMCM-41 , Cs-AlMCM-41 -basic TiMCM-41 ,V-MCM-41 -Redox
- 28. 2.Mesoporous Materials ascatalyst support • Noble metal supported catalyst supports Au-McM-41 , Pt- CMK-3 • Metal oxide supported catalysis Fe2O3- MCM-41 ,RuO2-SBA-15 • Metal complex supported catalysts Mn-Salen –SBA-15
- 29. 3. Application inenvironmental catalysis Immobilization of enzyme on Mesoporous Materials as catalysts Enzymes are excellent biocatalysts with high selectivity and efficiency in environment field, chemical and pharmaceutical industries are limited by their poor stability and chemical sensitivity
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- 32. 1) Sustained DrugRelease System Virtually any drug within a size range compatible with the size of the meso- channels has potential to be encapsulated and further deliver intracellularly. M. Vallet-Regi, et al. “A New Property of MCM-41: Drug Delivery System”, Chem. Mater. 2001, 13, 308-311.
- 33. 2. Mesoporous Materialsfor Bone Tissue Engineering
- 34. Mesoporous Bioactive scaffolds Scaffoldsare needed that can act as temporary templates for bone regeneration and actively stimulate vascularized bone growth so that bone grafting is no longer necessary. Bioactive glass is an ideal material because it rapidly bonds to bone and degrades over time, releasing soluble silica and calcium ions that are thought to stimulate osteoprogenitor cells.
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- 37. Pioneers in MesoporousMaterials Galen Stucky SBA-15 Fudan university FDU-11 Ryong Ryoo KIT -6 Hard template CMK materials P.Selvum IITM-56, NCCR-56
- 38. References: “On the ControllableSoft-Templating Approach to Mesoporous Silicates” Ying Wan and Dongyuan Zhao, chemical reviews, Volume 107, Number 7 . “Soft templating strategies for the synthesis of mesoporous materials: Inorganic, organic–inorganic hybrid and purely organic solids” Nabanita Pal, Asim Bhaumik, Advances in Colloid and Interface Science 189–190 (2013) 21–41 Thank you