Construction of heterogeneous frustrated lewis pairs based on covalent organic frameworks stabilized boron cations and investigation of cycloaddition reaction performance

Abstract

Frustrated Lewis Pairs (FLPs) catalysts have been widely designed and synthesized in current chemistry, with the key being the selection of boron-based Lewis acids. Among novel boron-based Lewis acids, boron cations with higher Lewis acidity caused by cationic charge have been proven to have special reactivity. However, the current boron cations have only been used to construct homogeneous FLPs, which would be difficult to meet the industrial process demand for FLPs catalysts, possibly due to the lack of suitable stabilizers. In this paper, we propose a strategy to construct heterogeneous FLPs using covalent organic frameworks (COFs) stabilized boron cations as Lewis acid. Firstly, heterogeneous Lewis acid COFs@[B(C6F5)2]+[Al2Cl7]- was prepared by stabilizing boron cations with CN bonds in COFs, followed by introducing tBu3P to construct heterogeneous FLPs COFs@[B(C6F5)2]+[Al2Cl7]-/tBu3P. Meanwhile, these FLPs catalysts exhibited excellent catalytic and cyclic performance in the preparation of cyclic carbonates by CO2 addition from epoxy compounds.