Structural characterization of alkyl bonded MCM-41 silica materials prepared by supercritical fluid approach

•MCM-41 silica spheres were prepared following the pseudomorphic synthesis.•Surface modification of MCM-41 was done using surface polymerization and supercritical fluid approach.•Surface coverages of materials were compared and found to be higher by supercritical fluid approach.•Pore dimensions of the materials were controlled by different silylating agents.•Characterization of these materials was done using nitrogen sorption, XRD, SEM, 29Si, 13C NMR and FTIR spectroscopies.

A comprehensive study is conducted on alkyl bonded mesoporous MCM-41 silica materials prepared using supercritical carbon dioxide (sc-CO2) as a bonding medium. The higher surface coverages of resulting materials as compared with organic solvent produced bonded phases are attributed to greater accessibility of the silica silanols in sc-CO2. The variation in pore dimensions depends on the nature of bonded alkyl chains. The resulting materials are characterized before and after surface modification using various characterization techniques. The specific surface area is calculated using BET method while information about pore diameter is obtained by DFT calculations. The degree of organization is investigated by XRD and SEM analysis gives information about morphology of the material. The degree of bonding and cross-inking of the alkylsilanes is determined by 29Si NMR spectroscopy. 13C NMR and FTIR spectroscopies are employed to study the conformational behavior and mobility of the bonded alky chains.

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