Spontaneous preparation of hierarchically porous silica monoliths with uniform spherical mesopores confined in a well-defined macroporous framework

Abstract

Hierarchically porous silica monoliths with well-defined interconnected macropores and uniform spherical mesopores were spontaneously prepared by combining polymerization-induced phase separation with an epoxide-mediated sol–gel route without any complicated aging and drying and high-temperature heat treatment. The precise control of pore structures can be realized by using propylene oxide (PO) as the gelation mediation agent, poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (P123) as the phase-separation inducer as well as the structure-directing agent and 1,3,5-trimethylbenzene (TMB) as the micelle-swelling agent. The as-prepared silica monolith possesses an interesting hierarchically porous structure constructed by 10 nm uniform spherical mesopores confined in a macroporous framework of well-defined 1 μm macropores, and exhibits a BET surface area as high as 848 m² g⁻¹. Heat treatment at 400–800 °C gradually decreases the BET surface area to 195 m² g⁻¹, while most of the uniform mesoporous structure remains intact.