Direct Syntheses of Ordered SBA-15 Mesoporous Silica Containing Sulfonic Acid Groups

Abstract

A simple procedure has been developed for the syntheses of functionalized mesoporous materials with sulfonic groups involving the co-condensation of tetraethoxysilane and mercaptopropyltrimethoxysilane in the presence of block copolymers and hydrogen peroxide under acidic conditions. The modified SBA-15 materials show hexagonal mesoscopic order and pore sizes up to 60 Å, with acid exchange capacities ranging from 1 to 2 mequiv of H+/g of SiO2, surface areas up to 800 m2/g, and excellent thermal and hydrothermal stabilities. The formation of the sulfonic groups during co-condensation of the silica species coincides with enhanced mesoscopic ordering and changes in the adsorption properties of the final materials. 31P MAS NMR measurements of chemically adsorbed triethylphosphine oxide confirm the presence of Brönsted acid centers that are stronger that those found in Al-MCM-41. Finally, this procedure has been generalized to prepare functionalized mesoporous solids containing sulfonic groups and other organic moieties.