Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500°C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35° to 80°C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140°C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) have been synthesized as crystals by copolymerization of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and -12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(Al) and the bridging O are replaced with transition metal ion and imidazolate link, respectively. In addition, one example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m 2 /g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents.

https://www.pnas.org/content/pnas/103/27/10186.full.pdf

Exceptional chemical and thermal stability of zeolitic imidazolate frameworks

It is possible to say that zeolites are the most widely used catalysts in industry They are crystalline microporous materials which have become extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis in the production of fine and speciality chemicals, particularly when dealing with molecules having kinetic diameters below 10 A The reason for their success in catalysis is related to the following specific features of these materials:1 (1) They have very high surface area and adsorption capacity (2) The adsorption properties of the zeolites can be controlled, and they can be varied from hydrophobic to hydrophilic type materials (3) Active sites, such as acid sites for instance, can be generated in the framework and their strength and concentration can be tailored for a particular application (4) The sizes of their channels and cavities are in the range typical for many molecules of interest (5-12 A), and the strong electric fields2 existing in those micropores together with an electronic confinement of the guest molecules3 are responsible for a preactivation of the reactants (5) Their intricate channel structure allows the zeolites to present different types of shape selectivity, ie, product, reactant, and transition state, which can be used to direct a given catalytic reaction toward the desired product avoiding undesired side reactions (6) All of these properties of zeolites, which are of paramount importance in catalysis and make them attractive choices for the types of processes listed above, are ultimately dependent on the thermal and hydrothermal stability of these materials In the case of zeolites, they can be activated to produce very stable materials not just resistant to heat and steam but also to chemical attacks Avelino Corma Canos was born in Moncofar, Spain, in 1951 He studied chemistry at the Universidad de Valencia (1967−1973) and received his PhD at the Universidad Complutense de Madrid in 1976 He became director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia in 1990 His current research field is zeolites as catalysts, covering aspects of synthesis, characterization and reactivity in acid−base and redox catalysis A Corma has written about 250 articles on these subjects in international journals, three books, and a number of reviews and book chapters He is a member of the Editorial Board of Zeolites, Catalysis Review Science and Engineering, Catalysis Letters, Applied Catalysis, Journal of Molecular Catalysis, Research Trends, CaTTech, and Journal of the Chemical Society, Chemical Communications A Corma is coauthor of 20 patents, five of them being for commercial applications He has been awarded with the Dupont Award on new materials (1995), and the Spanish National Award “Leonardo Torres Quevedo” on Technology Research (1996) 2373 Chem Rev 1997, 97, 2373−2419

From Microporous to Mesoporous Molecular-Sieve Materials and Their Use in Catalysis

Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly crystalline products (C3H2BO)6.(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6(3)/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 degrees to 600 degrees C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).

Porous, Crystalline, Covalent Organic Frameworks

The escalating level of atmospheric carbon dioxide is one of the most pressing environmental concerns of our age. Carbon capture and storage (CCS) from large point sources such as power plants is one option for reducing anthropogenic CO(2) emissions; however, currently the capture alone will increase the energy requirements of a plant by 25-40%. This Review highlights the challenges for capture technologies which have the greatest likelihood of reducing CO(2) emissions to the atmosphere, namely postcombustion (predominantly CO(2)/N(2) separation), precombustion (CO(2)/H(2)) capture, and natural gas sweetening (CO(2)/CH(4)). The key factor which underlies significant advancements lies in improved materials that perform the separations. In this regard, the most recent developments and emerging concepts in CO(2) separations by solvent absorption, chemical and physical adsorption, and membranes, amongst others, will be discussed, with particular attention on progress in the burgeoning field of metal-organic frameworks.

Carbon Dioxide Capture: Prospects for New Materials

MCM-41 siliceous molecular sieves were used to test the applicability of the Kelvin equation for nitrogen adsorption in cylindrical pores of the size from 2 to 65 nm It was shown that the Kelvin equation for the hemispherical meniscus, corrected for the statistical film thickness, is in quite good agreement with an experimental relation between the pore size and the capillary condensation pressure The agreement can be made quantitative in the pore size range from ca 2 to 65 nm, if a simple correction to the Kelvin equation is introduced The required statistical film thickness curve (t-curve) was calculated using nitrogen adsorption data for large pore MCM-41 samples and the obtained results were extrapolated using an adsorption isotherm for a macroporous silica gel Moreover, an accurate analytical representation of the t-curve was found Since both the corrected Kelvin equation for cylindrical pores and the t-curve have simple analytical forms, they can conveniently be used in a variety of methods 

Application of large pore MCM-41 molecular sieves to improve pore size analysis using nitrogen adsorption measurements

The area of periodic mesoporous materials prepared by cooperative assembly in the presence of amphiphile molecules underwent dramatic growth. Among the silica-based materials, many types may be reg...

Periodic Mesoporous Silica-Based Organic−Inorganic Nanocomposite Materials

Crystalline mesoporous molecular sieves may be prepared under a wide range of conditions in the presence of cationic, anionic, gemini, or neutral surfactants. These mesostructured materials include pure and modified silicates, other metallic oxides and sulfides as well as aluminophosphates. Air calcination of silicate-based mesoporous molecular sieves with stable frameworks (MCM-41, MCM-48, SBA-n, MSU-n) affords materials with extremely high surface areas. Their pore size may be adjusted from ca. 20 to more than 100 A using different strategies. Because of their unique flexibility in terms of synthesis conditions, pore size tuning, and framework composition, these materials have been targeted for a number of potential applications, particularly in catalysis. The present review deals with the fast-growing area of catalysis by crystalline mesoporous materials. Three topics are discussed separately:  (i) acid catalysis, (ii) redox catalysis, and (iii) miscellaneous applications. Particular attention is put o...

Catalysis by Crystalline Mesoporous Molecular Sieves

This review article deals with recent progress in the preparation of sulfated zirconia (SZ)-bassed, strong solid-acid catalysts, the characterization of their physicochemical properties and the evaluation of their catalytic performance in various promising applications. Strong emphasis was put on discussion of controversial issues such as the strength of acid sites, the nature of active sites, the reaction mechanism, and the role and state of supported platinum. An important part of this work was devoted to recent catalytic applications.

Sulfated Zirconia-Based Strong Solid-Acid Catalysts: Recent Progress

CO2 adsorption−desorption cycles and the corresponding mechanisms over amine supported CO2 adsorbent (TRI-PE-MCM-41) under dry conditions and in the presence of moisture (20 °C as dew point).

Abdelhamid Sayari

Papers

Application of large pore MCM-41 molecular sieves to improve pore size analysis using nitrogen adsorption measurements

Periodic Mesoporous Silica-Based Organic−Inorganic Nanocomposite Materials

Catalysis by Crystalline Mesoporous Molecular Sieves

Sulfated Zirconia-Based Strong Solid-Acid Catalysts: Recent Progress

Stabilization of Amine-Containing CO2 Adsorbents: Dramatic Effect of Water Vapor