Ultrahigh CO2 capture and separation in 3D Cage-COFs: Synergistic effect from Li, topology, and pore size

Abstract

The urgency of mitigating excessive CO2 emissions has promoted the development of CO2 adsorbents. Three-dimensional Cage-Covalent organic frameworks (3D Cage-COFs) are excellent candidates due to their outstanding pore features and diversified adjustability. Herein, CO2 capture and separation performances in 3D Cage-COFs modified by metal Li, topology, and pore size were investigated by Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT). It is shown that the introduction of Li enhanced structural polarity and provided efficient CO2 adsorption sites. Topological structure regulation optimized the space utilization and adsorption site distribution. Moreover, pore size adjustment mitigated adsorption site blockages caused by Li and topological regulation. With the synergistic effect of the above modifications, COF-3fold-OLi2 exhibited the highest CO2 capture capacity of 236.10 cm3 cm−3 with a selectivity of 205.87/94.37 over N2/CH4 (v: v = 50: 50) at 298 K and 1.0 bar. The synergistic effect of metal Li, topology, and pore size on improving CO2 capture and separation performances was illustrated through structural stability, pore characteristics, gas distribution, adsorption configuration, radial distribution function, isothermal adsorption heat, and interactions. These insights are essential for developing adsorbent materials for CO2 capture and separation.