A New Synthetic Route to Microporous Silica with Well-Defined Pores by Replication of a Metal-Organic Framework

Microporous amorphous hydrophobic silica materials with well-defined pores were synthesized by replication of the metal-organic framework (MOF) [Cu₃(1,3,5-benzenetricarboxylate)₂] (HKUST-1). The silica replicas were obtained by using tetramethoxysilane or tetraethoxysilane as silica precursors and have a micro-meso binary pore system. The BET surface area, the micropore volume, and the mesopore volume of the silica replica, obtained by means of hydrothermal treatment at 423K with tetraethoxysilane, are 620m²g^-1, 0.18mLg^-1, and 0.55mLg^-1, respectively. Interestingly, the silica has micropores with a pore size of 0.55nm that corresponds to the pore-wall thickness of the template MOF. The silica replica is hydrophobic, as confirmed by adsorption analyses, although the replica has a certain amount of silanol groups. This hydrophobicity is due to the unique condensation environment of the silica precursors in the template MOF.