A method for the preparation of transparent mesoporous silica sol–gel monoliths containing grafted organic functional groups

Abstract

Transparent, crack-free mesoporous silica sol–gel monolith 2 was prepared from the hydrolysis of Si(OMe)4 in MeOH containing ethylene glycol (HOCH2CH2OH). Gradual exposure of the product monolith 1 to MeOH/H2O and then H2O helps prevent cracking of the monolith. Direct reaction of chelating diamine H2N(CH2)2NH(CH2)3Si(OMe)3 with 1 gave diamine-grafted monolith 3. Imprint-grafting of monolith 1 with the Cu2+ complex Cu[H2N(CH2)3Si(OMe)3]42+ yielded monolith 5 grafted with the monoamine ligand H2N(CH2)3Si(O–)3 (APS). BET studies showed that the average pore size in amine-imprint-grafted 5 was ca. 47 Å with a specific surface area of 232 m2 g−1, and the total pore volume was 0.24 cm3 g−1 for all pores of the gel which were less than 174 Å.