Separating acetylene from carbon dioxide is important but highly challenging due to their similar molecular shapes and physical properties. Adsorptive separation of carbon dioxide from acetylene can directly produce pure acetylene but is hardly realized because of relatively polarizable acetylene binds more strongly. Here, we reverse the CO2 and C2H2 separation by adjusting the pore structures in two isoreticular ultramicroporous metal−organic frameworks (MOFs). Under ambient conditions, copper isonicotinate (Cu(ina)2), with relatively large pore channels shows C2H2‐selective adsorption with a C2H2/CO2 selectivity of 3.4, whereas its smaller‐pore analogue, copper quinoline‐5‐carboxylate (Cu(Qc)2) shows an inverse CO2/C2H2 selectivity of 5.6. Cu(Qc)2 shows compact pore space that well matches the optimal orientation of CO2 but is not compatible for C2H2. Neutron powder diffraction experiments confirmed that CO2 molecules adopt preferential orientation along the pore channels during adsorption binding, whereas C2H2 molecules bind in an opposite fashion with distorted configurations due to their opposite quadrupole moments. Dynamic breakthrough experiments have validated the separation performance of Cu(Qc)2 for CO2/C2H2 separation.

中文翻译：

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二氧化碳和乙炔在两种同构吡啶-羧酸铜骨架中的反向分离

从二氧化碳中分离乙炔很重要，但由于其相似的分子形状和物理性质而极具挑战性。二氧化碳与乙炔的吸附分离可以直接生产纯乙炔，但由于相对可极化的乙炔结合更牢固，因此很难实现。在这里，我们通过调整两个等孔超微孔金属有机框架（MOF）中的孔结构来逆转CO2和C2H2的分离。在环境条件下，具有相对较大孔道的异烟酸铜 (Cu(ina)2) 表现出 C2H2 选择性吸附，C2H2/CO2 选择性为 3.4，而其较小孔的类似物喹啉-5-羧酸铜 (Cu(Qc) )2) 显示逆 CO2/C2H2 选择性为 5.6。 Cu(Qc)2 显示出致密的孔隙空间，与 CO2 的最佳方向很好地匹配，但与 C2H2 不相容。中子粉末衍射实验证实，CO2分子在吸附结合过程中沿孔道优先取向，而C2H2分子则以相反的方式结合，由于其相反的四极矩而导致构型扭曲。动态突破实验验证了Cu(Qc)2用于CO2/C2H2分离的分离性能。