Microwave synthesis of hierarchical porous materials with various structures by controllable desilication and recrystallization

Abstract

Hierarchical porous materials with controllable structures are efficiently synthesized through a one-step approach by adjusting the detemplation degree of the parent zeolites. Partial removal of the template from the micropores provides an opening framework in ZSM-5 for subsequent desilication in alkaline solution by microwave digestion, while the template-containing regions are restrained from silicon leaching. OH− ions are consumed during Si leaching to provide favorable pH for the crystallization of mesoporous structures. Consequently, mesoporous silica shells are coated on the partially detemplated zeolites to form the hierarchical structures, and the parent microporous core with the residual template is immune to desilication. The structures of the hierarchical porous materials are susceptible to the detemplation degree of the pristine zeolite. The surface area and pore volume of the hierarchical porous materials are enhanced greatly compared with those of the pristine ZSM-5 because of the large contribution of the mesopores.