Selectively separating CH₄ from N₂ in coal‐mine methane is significantly important in the chemical industry, but challenging and energy‐intensive. Using porous materials as adsorbents can separate CH₄/N₂ mixtures with low energy consumption, but most adsorbents encounter the problem of poor separation selectivity. Here, we propose a strategy for improving CH₄/N₂ 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 CH₄ over N₂. At 298 K and 100 kPa, CAU‐21‐BPDC with four highly symmetric polar sites in the pore walls exhibits 2.4 times higher CH₄/N₂ selectivity than CAU‐8‐BPDC without four highly symmetric polar sites. Gas adsorption isotherms, CH₄/N₂ selectivity calculations, Q _st of CH₄, interaction energy calculations, adsorption density distributions of CH₄ and N₂, and breakthrough curves reveal that CAU‐21‐BPDC is a potential candidate for selective capture coal‐mine methane.

中文翻译：

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提高异构铝基MOF中的CH4 / N2选择性，以高度选择性地捕获煤矿甲烷

在化学工业中，从煤甲烷中的N ₂中选择性地分离CH ₄与N ₂极为重要，但具有挑战性且耗能巨大。使用多孔材料作为吸附剂可以以较低的能耗分离CH ₄ / N ₂混合物，但是大多数吸附剂都遇到分离选择性差的问题。在这里，我们提出了一种通过控制两个具有四个高度对称极性位的异构铝基金属有机骨架（MOF）中的孔壁环境来改善CH ₄ / N ₂选择性的策略，以增强对N _2的CH ₄吸附亲和力。。在298 K和100 kPa时，孔壁中具有四个高度对称极性位点的CAU-21-BPDC的CH ₄ / N ₂选择性是没有四个高度对称极性位点的CAU-8-BPDC的2.4倍。气体吸附等温线，CH ₄ / N ₂选择性计算，CH _4的Q _st，相互作用能计算，CH ₄和N _2的吸附密度分布以及穿透曲线表明，CAU-21-BPDC是选择性捕集煤的潜在候选者-甲烷。