Structural regulation of ionic covalent organic frameworks for enhanced CO 2 capture and catalytic conversion †

Abstract

Ionic covalent organic frameworks (COFs), a subclass of ionic porous crystalline materials, have emerged as promising candidates for CO2 capture and catalytic conversion. However, most reported ionic COFs rely on frameworks linked by reversible covalent bonds (e.g., imine -C=N-), which compromises their structural stability and limits practical applications.To overcome these limitations, this work employs an industrially scalable and robust olefin-linked COF, NKCOF41, as a platform for constructing three ionic COFs (NKCOF41 + -C2H5Br ‾ , NKCOF41H + -Br ‾ , and NKCOF41 + -C2H4OHBr ‾ ) via quaternization and protonation strategies. These ionic derivatives preserve high crystallinity and specific surface area.Among them, NKCOF41 + -C2H4OHBr ‾ exhibits exceptional CO2 adsorption capacity (3.94 mmol g ‾1 , 72% higher than neutral NKCOF41), attributed to the synergistic effect of CO2-philic -OH groups, Br ‾ sites, and a cationic framework. Comparative catalytic studies reveal that NKCOF41 + -C2H4OHBr ‾ markedly enhances the CO2 cycloaddition reaction, achieving a 95.3% cyclic carbonate yield under solvent-free and co-catalyst-free conditions (100 o C, 0.5 MPa, 24 h), along with excellent recyclability over six cycles without activity loss. This study presents a simple, scalable, and broadly applicable strategy for the design of high-performance, task-specific, and structurally stable ionic COFs.