Modification of the adsorption and catalytic properties of micro- and mesoporous materials by reactions with organometallic complexes

Abstract

This review describes the work of two laboratories in the field of the modification of micro-and mesoporous molecular sieves through reactions with organometallic complexes. The modification of zeolites can occur inside the pore channels or on the external surface, depending on the size of the organometallic complex. When the modification occurs on the external surface, it results in a decrease of the pore entrance, which will lead in turn to a modification of the sorption properties of the zeolite, by decreasing the rate of the adsorption (mainly by a kinetic control). Such a material can be also used in catalysis, because the external acid sites, which are responsible for side-reactions, have been removed upon grafting. When small organometallic complexes are used, they can fill the channels and cages of the zeolite and react with internal hydroxyl groups. Due to the high acidity of zeolites, the reaction occurs very easily (for example at 100 °C on faujasite), in contrast to what is observed on the external surface, therefore leading to high metal loadings. In that case, the modification of the sorption properties will be mainly related to a thermodynamic control. The resulting materials can be useful in catalysis, by combining the activity of the organometallic complex and properties (for example shape-selectivity) of the zeolite. Modification of mesoporous molecular sieves occurs always in the pores and results in altering of the sorption properties of the solid, by changing the interaction type between the sorbent and the sorbate. For example the sorption isotherm of alkanes is changed from type II to type III according to the IUPAC nomenclature. zeolites, transition metals, organometallic compounds, adsorption properties

Thiol group functionalization of mesoporous SiO 2 SBA-15 using supercritical CO 2

“…Chemical modification of metal oxide surfaces is performed to improve the physical and chemical properties of the materials such as roughness, hydrophilicity, surface energy, biocompatibility, reactivity… It is currently used to prepare stationary phases in chromatography, [1] biocompatible surfaces, [2] environmental sorbents, [3,4] heterogeneous catalysts [5] and sensors [6] among others. Stabilization of metal nanoparticles is also performed by functionalization with organic ligands.…”

Micro, Meso and Macro Porous Materials on Medicine

“…On some porous materials like zeolites, the surface modification can occur inside the pore channels or on the external surface, depending on the size of the organometallic complex or functional group. When the modification occurs on the external surface, it results in a decrease of the pore entrance, which lead in turn to a modification of the sorption properties of the micro or mesoporous matrix, by decreasing the rate of the adsorption (mainly by kinetic control) [19]. This interactions between the matrix and the adsorbed molecule could be study by the combination of the two techniques provides the first direct proof, the molecule diffusion pathway through the pore system correlates with the orientation, the influence of specific structural features of the host on the diffusion behavior of the guest molecules can be clearly seen with a single fluorescent dye molecule application, how it changes speed in channel structure, and how it bounces off domain boundary.…”