Ionic Liquid‐Confined Covalent‐Organic Framework Pores as Nanoreactors for CO ₂ Photoconversion

Abstract

Abstract The topological nanopores of covalent organic frameworks (COFs) show promise as spatially confined nanoreactors for solar CO 2 photoconversion. However, simultaneously increasing the electron density, improving the electron transfer, CO 2 capture, and catalytic efficiency within nanopores remains a challenge for optimizing the performance of such nanoreactors. Here, micro‐ and mesoporous triazine‐COFs were in situ grown on amino‐modified BiVO 4 nanosheets (BVO), respectively, obtaining two‐dimensional heterojunctions. A highly active ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf 2 ]) was subsequently confined within COF nanopores. Adopting IL‐confined COF mesopore‐nanoreactors, the best nanocomposite enables a 38‐fold photoactivity enhancement compared to BVO and 100% selectivity towards CO and CH 4 in pure water under UV‐vis light irradiation, resulting in the record apparent quantum yield of 12.7% in visible region. Such performance is due to increased electron density inside mesopores via Z‐scheme charge separation between BVO and COF, and the nanoconfinement effects of mesopores for IL, leading to i) facilitated directed electron transfer from COF to IL via multi‐hydrogen bonds between the triazine acceptors and [EMIM] + cations, ii) promoted CO 2 capture by redistribution of IL ions, and iii) easy activation of CO 2 molecules owing to shortened distance to adjacent [EMIM] + cations as catalytic sites and reduced relative orientation angle.