Rate of Access to the Binding Sites in Organically Modified Silicates. 3. Effect of Structure and Density of Functional Groups in Mesoporous Solids Obtained by the Co-Condensation Route

Abstract

Mercaptopropyl-functionalized silica spheres have been prepared by self-assembly co-condensation of mercaptopropyltrimethoxysilane (MPTMS) and tetraethoxysilane (TEOS) precursors in the presence of a cationic surfactant as templating agent and ammonia as catalyst. Several materials have been obtained by varying the MPTMS content from 5 to 100% in the synthesis medium, giving rise to a wide range of porous solids featuring different functionalization levels (denoted MPS-n%, with n ranging from 5 to 100) and distinct structural order/disorder over different length scales. They were characterized by N2 sorption isotherms, XRD, scanning and transmission electron microscopy, and particle size analysis. Their reactivity in aqueous media was studied with respect to their binding properties toward HgII species by complexation with thiol groups. Total accessibility (expressed on the basis of a 1:1 S/Hg stoechiometry) was demonstrated and quantified for well-ordered materials containing up to 30% MPTMS. Less open s...