Biguanide-functionalized hierarchical porous covalent organic frameworks for efficient catalysis of condensation reactions

Abstract

• A covalent organic framework bearing biguanide (DG-COF) was successfully fabricated with specific hierarchical structure. • DG-COF was employed as heterogeneous basic catalyst for the Knoevenagel condensation and Knoevenagel-Michael-cyclocondensation reaction under mild reaction conditions. • DG-COF exhibited high catalytic activity and high stability. Covalent organic frameworks (COFs) can be rationally designed with desired physicochemical properties for a far-ranging application in catalytic systems. Herein, a biguanide-functionalized covalent organic framework was designed and prepared via N -alkylation reaction, exhibiting a granular aggregate structure with high specific surface area. The biguanide-decorated DG–COF can be used as a highly efficient basic catalyst for the Knoevenagel condensation and Knoevenagel-Michael-cyclocondensation reaction. The present methodology is of excellent yields, short reaction times and simple operational procedure. DG–COF catalytic performance does not change after eight-times regeneration. In this paper, we reported that a covalent organic framework bearing biguanide (DG-COF) was controllably fabricated with specific hierarchical structure. DG-COF exhibited high catalytic activity as a heterogeneous basic catalyst for the Knoevenagel condensation and Knoevenagel-Michael-cyclocondensation reaction. The recycled DG-COF could retain good catalytic stability even after eight cycles of use.