A CO2-expanded gelation approach to prepare bimodal porous silica materials and their catalytic applications

Abstract In this work, a facile route was designed to fabricate bimodal porous silica with high surface area and pore volume via a CO 2 -expanded gelation with assistance of CTAB. Parameters such as the amount of CTAB, pressure of CO 2 and agitation time were investigated and optimized. Results showed bimodal silica contained small pore size (around 2 nm) from CTAB templating and large pore size (> 4 nm) from CO 2 -expanded gelation could be easily adjusted by the synthesis conditions. A typical sample with surface area of 1133 m 2 /g and pore volume of 1.24 mL/g was applied as a catalyst support for phosphotungstic acid, revealing much faster catalysis rate and relatively high selectivity for 1, 8-cineole from α-terpineol than the commercial MCM-41. The approach was also successfully extended to the preparation of bimodal NiO/silica composite, and the reduced Ni/silica showed higher catalysis performance than the unimodal sample for phenol hydrogenation to cyclohexanol.