In situ polymerization of poly(vinylimidazole) into the pores of hierarchical ZSM-5zeolite as an acid–base bifunctional catalyst for cascade reaction

Poly(vinylimidazole)/hierarchical ZSM-5 has been prepared as a novel and efficient acid–base bifunctional catalyst bya simple method. First, the hierarchical ZSM-5 zeolite was synthesized by an indirect method from KIT-6 as a silicasource. By this method, control of the zeolite crystallization was achieved due to the adjustment transformationprocessing of amorphous mesoporous silica to zeolite crystal. Then, vinylimidazole as a basic part was polymerized byan in situ method into the zeolite’s pores. This acid–base bifunctional heterogeneous catalyst was characterized by FTIR,TG-DTG, N2 adsorption–desorption, TEM, SEM, NH3- TPD, and XRD. The catalyst has been applied to one-potC–C bond formation tandem cascade reactions condensation by the simple method at low temperature. Due to theuniform distribution of poly(vinylimidazole) in the micro-meso pores of the hierarchical zeolite reactants, the productseasily pass through the catalytic active sites. The co-existence of acidic and basic sites in the structure of the catalysthas a crucial role in the superior activity of this catalyst. Moreover, the catalyst showed excellent recyclability and highactivity even after 7 runs with only a 10% reduction in activity being detected.

Keywords:

Hierarchical ZSM-5 , Acid–base bifunctional catalyst , Poly(vinylimidazole) , Deacetalization–Henryreaction , Deacetalization–Aldol condensation