CO₂ removal is a critical step in natural gas purification to upgrade the gas stream for practical use. Although covalent organic frameworks (COFs) show promise for gas separation, research in this area remains in its early stages, and their separation performance requires further improvement. Here, a combined quantum chemical calculations and molecular dynamics simulations were performed to elucidate the fundamental mechanisms governing CH₄/CO₂ separation in COF materials. Calculated results demonstrated that the adsorption of CO₂ within the one-dimensional (1D) channels of COF10 is more favorable than that of CH₄, and the adsorption selectivity (S_ads) exhibits a significant enhancement by Cl-functionalization. Moving rate of CH₄ is much larger than that of CO₂ in the 1D channel of COF10, and Cl-functionalization creates stronger diffusion barriers for CO₂ than for CH₄. Cl-functionalized COFs exhibit substantially stronger CH₄/CO₂ selectivity than COF10. It is verified that the interaction energies of more polarized CO₂ on the pore wall of COF10 are larger than those of CH₄, and the increased polarity induced by the highly electronegative Cl groups strengthens the framework’s affinity for gas molecules. As a result, improved CO₂/CH₄ selectivity of COF10 by Cl-functionalization can be explained.

Single-atom catalysts based on metal–N–C constituents facilitate oxygen reduction reaction kinetics due to super-high atomic utilization efficiency. However, conventional isolated atoms suffer from coordination symmetry and make less use of electron interaction between adjacent metal sites, which severely impedes its electrocatalytic activity. In response, we creatively issue a feasible potassium hydroxide clipping strategy through breaking up partial Co–N bonding and reconstructing Co–Co coordination, thus simultaneously implanting abundant Co atomic clusters and Co single atoms (SAs) on the surface of covalent organic framework (COF)-derived N-doped carbon nanospheres, which are intertwined by surrounding carbon nanotube (CNT) networks. This elaborately designed Co_AC-SAs/N–C@CNT catalyst combines the benefits of the asymmetrically coordinated Co–N₂ configuration and Co–Co electronic interaction, which exert great influence on local atomic microenvironment of metal sites and, thus, efficiently modulate the electronic structure. Then, the optimized d-band center of Co centers contributes to weakening oxygen intermediate adsorption and to reducing the rate-determining step energy barrier. Meanwhile, because of the unique surface chelation mechanism between COF matrix and Co cations, the as-optimized Co centers are homogenously stabilized on the carbon outermost shell, further maximizing active sites efficiency. As expected, the Co_AC-SAs/N–C@CNT catalyst harvests superior oxygen reduction reaction catalytic kinetics in alkaline medium, surpassing the commercial Pt/C catalyst.