Efficient C2H2 Separation from CO2 and CH4 within a Microporous Metal–Organic Framework of Multiple Functionalities

The separation of acetylene (C2H2) from carbon dioxide (CO2) and methane (CH4) is of great significance, but remains challenging, because of their similar physicochemical properties, and it currently has received substantial research interest by using adsorptive separation based on metal–organic frameworks (MOFs). Herein, a new microporous Cu-MOF, [Cu(5-OH-IPA2–)(DPYA)(H2O)] (BUT-318, where 5-OH-IPA2– = 5-hydroxyisophthalate and DPYA = 4,4′-dipyridylamine) has been synthesized successfully under solvothermal conditions, which exhibits excellent separation performance for C2H2/CO2 and C2H2/CH4 gas mixtures. The presence of Cu(II) open metal sites and different Lewis base sites (−OH and −NH) make the activated BUT-318 efficiently bind C2H2 and exhibit high adsorption capacity under low pressure (24.52 and 9.1 cm3 g–1 under 0.01 bar, at 273 and 298 K, respectively). The corresponding IAST (ideal adsorbed solution theory) selectivity was 9.8 and 244.3 at 273 K and 1 bar for an equimolar C2H2/CO2 and C2H2/CH4 mixture. The separation performance and reusability under dynamic conditions were also confirmed by column breakthrough experiments, making BUT-318a a promising candidate for the practical C2H2 separation.从乙炔（C₂H₂）与二氧化碳（CO₂）、甲烷（CH₄）的分离因三者理化性质相近，既具有重要研究价值又极具挑战性，目前基于金属有机框架（metal–organic frameworks, MOFs）的吸附分离策略已受到学界广泛关注。本文通过溶剂热法成功合成了一种新型微孔Cu基MOF，其化学式为[Cu(5-OH-IPA²⁻)(DPYA)(H₂O)]，命名为BUT-318（其中5-OH-IPA²⁻为5-羟基间苯二甲酸根，DPYA为4,4'-二吡啶胺）。该材料对C₂H₂/CO₂与C₂H₂/CH₄混合气体展现出优异的分离性能。活化后的BUT-318存在Cu(II)开放金属位点与两类路易斯碱位点（-OH与-NH），可高效结合乙炔分子，并在低压条件下展现出高吸附容量：在273 K、0.01 bar时吸附量达24.52 cm³·g⁻¹，298 K、0.01 bar时达9.1 cm³·g⁻¹。对于等摩尔比的C₂H₂/CO₂与C₂H₂/CH₄混合气体，在273 K、1 bar条件下，基于理想吸附溶液理论（ideal adsorbed solution theory, IAST）计算得到的选择性分别为9.8与244.3。柱穿透实验进一步证实了该材料在动态条件下的分离性能与循环复用性，表明BUT-318a是一种极具实际应用潜力的乙炔分离候选材料。