Improving CH4/N2 selectivity within isomeric Al‐based MOFs for the highly selective capture of coal‐mine methane

Abstract Selectively separating CH 4 from N 2 in coal‐mine methane is significantly important in the chemical industry, but challenging and energy‐intensive. Using porous materials as adsorbents can separate CH 4 /N 2 mixtures with low energy consumption, but most adsorbents encounter the problem of poor separation selectivity. Here, we propose a strategy for improving CH 4 /N 2 selectivity by controlling pore wall environment in two isomeric Al‐based metal–organic frameworks (MOFs) with four highly symmetric polar sites for strengthened adsorption affinity toward CH 4 over N 2 . At 298 K and 100 kPa, CAU‐21‐BPDC with four highly symmetric polar sites in the pore walls exhibits 2.4 times higher CH 4 /N 2 selectivity than CAU‐8‐BPDC without four highly symmetric polar sites. Gas adsorption isotherms, CH 4 /N 2 selectivity calculations, Q st of CH 4 , interaction energy calculations, adsorption density distributions of CH 4 and N 2 , and breakthrough curves reveal that CAU‐21‐BPDC is a potential candidate for selective capture coal‐mine methane .