Covalent organic frameworks functionalization with ionic liquid and single metal ions for CO2 capture and cycloaddition under mild condition.

The ecofriendly conversion of captured CO2 is crucial for global sustainable development. However, direct conversion of CO2 into value-added chemical feedstocks at atmospheric pressure remains challenging due to its thermodynamic stability and kinetic inertness. Herein, we report a new type of catalyst with low catalytic energy barrier, synthesized by post-modifying supercritical CO2-activated imine-linked triazine-based covalent organic framework (TAPT-COF) through the covalent attachment of ionic liquid (IL) and coordination of Zn ion within its pores. The resulting catalyst, referred to as IL-Zn-COF, exhibits CO2 adsorption capacity of 31.2 mg g-1 at 298 K, enabling CO2 enrichment near active sites and supporting direct CO2 conversion. Consequently, IL-Zn-COF achieves a high cyclochloroallyl carbonate yield of 99.0 % at 1 bar and 60 °C without co-catalysts. Experimental results and density functional theory (DFT) calculations confirm that the cooperation of Zn2+ and Br- dramatically expedites the rate-limiting step of cycloaddition, outperforming the individual catalytic components of ZnCl2 and ILs. Compared with the physically impregnated system (a mixture of IL and Zn-coordinated COF), IL-Zn-COF demonstrates an 16.1 % increase in catalytic activity for cycloaddition. Importantly, the catalyst maintains its activity over ten cycles. Additionally, IL-M-COFs (M = Mn, Co, Ni) are also synthesized to further evaluate the effects of different metal ions on CO2 capture and conversion performance.