Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), Valais Wallis, CH-1951 Sion, Switzerland.
Dalton Trans. 2018 Aug 7;47(31):10527-10535. doi: 10.1039/c8dt01247d.
Metal-organic frameworks (MOFs) are porous, tunable crystalline materials that are attracting widespread scientific attention for their potential use in post-combustion CO2 capture. In this work, we report the synthesis of a new ligand, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate, H2Sp5-BF4, that is subsequently used for the construction of a novel MOF, Cu-Sp5-EtOH. This highly crystalline material has a charged framework that is expected to give rise to high CO2/N2 selectivity. However, the pores of the parent structure could not be accessed due to the presence of strongly coordinated ethanol molecules. After solvent exchange with methanol and subsequently heating Cu-Sp5-MeOH under vacuum, we are able to liberate the solvent providing other small molecules like CO2 access to the inside of the now porous structure, Cu-Sp5. The combination of open metal sites and framework charge leads to an exceptionally high CO2/N2 selectivity, as determined by Ideal Adsorbed Solution Theory (IAST) calculations performed on single-component adsorption isotherms. The CO2/N2 selectivity of Cu-Sp5 reaches a value of over 200 at pressures typically found in post-combustion flue gas (0.15 bar CO2/0.85 bar N2), a value that is among the highest reported to date.
金属-有机骨架（MOFs）是多孔、可调谐的结晶材料，由于其在燃烧后 CO2 捕集方面的潜在应用而受到广泛关注。在这项工作中，我们报告了一种新配体 1,3-双（4-羧基苯基）-4,5-二氢-1H-咪唑-3-鎓四氟硼酸盐（H2Sp5-BF4）的合成，随后用于构建一种新型的 MOF，Cu-Sp5-EtOH。这种高结晶材料具有带电荷的骨架，预计会产生高的 CO2/N2 选择性。然而，由于强配位的乙醇分子的存在，母体结构的孔无法进入。在用甲醇进行溶剂交换后，Cu-Sp5-MeOH 在真空下加热，我们能够释放出溶剂，使其他小分子如 CO2 能够进入现在具有多孔结构的 Cu-Sp5 内部。开放的金属位点和骨架电荷的结合导致了极高的 CO2/N2 选择性，这是通过对单组分吸附等温线进行理想吸附溶液理论（IAST）计算得出的。在燃烧后烟道气中通常发现的压力（0.15 巴 CO2/0.85 巴 N2）下，Cu-Sp5 的 CO2/N2 选择性达到 200 以上，这是迄今为止报道的最高值之一。
