Acid and base coexisted heterogeneous catalysts supported on hypercrosslinked polymers for one-pot cascade reactions

Heterogeneous microporous acid (sulfonic acid) and base (benzylamine) catalysts with high surface areas were synthesized using simple aromatic compounds through one-step external cross-linking reaction. The direct induction and control of catalytic sites were achieved by functionalized monomers using an appropriate amount of acid/base monomers. This strategy provides an easy approach to produce highly stable and acid/base functionalized microporous organic polymers. The structure and composition of the catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, Fourier transform infrared spectroscopy (FT-IR), solid-state C-13 cross polarization magic angle spinning (CP/MAS) NMR, thermogravimetric analysis (TGA), and element mapping analysis. The stable porous skeleton and the accurate manipulation of the catalyst structure allowed us to use the obtained polymers as compatible and efficient acid/base co-catalysts for one-pot cascade reactions. We demonstrated the use of these microporous heterogeneous catalysts for the cascade deacetalization/Henry and deacetalization/Knoevenagel reactions. The results demonstrated that preparing microporous materials from simple aromatic compounds through one-step external cross-linking reaction is indeed a cost-effective and easy-to-handle method to produce functionalized heterogeneous catalysts. The microporous heterogeneous catalysts produced by this method are highly stable and the amount of catalytically active sites can easily be controlled to form a catalytic system with two antagonistic centers. (C) 2017 Elsevier Inc. All rights reserved.