For the cycloaddition of CO2 to cyclic carbonates to become a practical chemical means of achieving carbon neutrality, the development of efficient and selective catalysts is essential yet highly challenging. Here, we rationally design two zinc-based covalent organic framework (COF) catalysts featuring zinc–nitrogen (Zn–N) active sites and different bromide site configurations via a simple solvothermal strategy. We systematically investigate the influence of bromide configurations of COFs on CO2 cycloaddition performance. Notably, the optimum Zn-COF-366@OC2Br achieves an excellent yield of over 99% in the cycloaddition of CO2 and propylene oxide (PO) to propylene carbonate (PC) under cocatalyst-free conditions. Density functional theory calculations reveal that the energy barriers for ring-opening and the CO2 attacking step on Zn-COF-366@OC2Br are much lower than those on referenced Zn-COF-366@Br, highlighting the crucial role of flexibility of bromine. This work offers an insight into the modular design of highly active catalysts for the important acid–base catalyzed reactions.
Chen et al. (Wed,) studied this question.