Covalent organic frameworks functionalization with ionic liquid and single metal ions for CO₂ capture and...

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.