Modeling the selectivity of indoor pollution gases over N2 on covalent organic frameworks

The selectivity of indoor pollution gases (including formaldehyde, benzene, and toluene) over N-2 on a set of 37 covalent organic frameworks (COFs) was modeled by combining classical grand canonical Monte Carlo (GCMC) methods and periodic density functional theory with dispersion correction (DFT-D2). The pore volume, pore size, and the isosteric heat (Q(st)) of gases on COFs were investigated to explore the origin of the high selectivity of pollution gases over N-2. We found that the size match between the pore of the COFs and the corresponding pollution gases is the key factor for high selectivity. Additionally, the Q(st) for the investigated four gases follows the order of toluene>benzene>formaldehyde>N-2, which is consistent with the order of selectivity. Furthermore, the favorite sites and interaction energies of pollution gases on COFs were calculated by the periodic DFT-D2 method. Our simulation procedure offers an alternative approach with which to evaluate or design the best candidate porous materials in capture pollution gases.