A Microporous Metal–Organic Framework with Lewis Basic Nitrogen Sites for High C2H2 Storage and Significantly Enhanced C2H2/CO2 Separation at Ambient Conditions

A novel metal–organic framework (MOF), [Cu2L­(H2O)2]·7DMF·4H2O [ZJU-40; H4L = 5,5′-(pyrazine-2,5-diyl)­diisophthalic acid], with Lewis basic nitrogen sites has been constructed and structurally characterized. Owing to the combined features of high porosity, moderate pore sizes, and immobilized Lewis basic nitrogen sites, the activated ZJU-40a exhibits the second-highest gravimetric C2H2 uptake of 216 cm3 g–1 (at 298 K and 1 bar) among all of the reported MOFs so far. This value is not only much higher than that of the isoreticular NOTT-101a (184 cm3 g–1), but also superior to those of two very promising MOFs, known as HKUST-1 (201 cm3 g–1) and Co-MOF-74 (197 cm3 g–1). Interestingly, the immobilized nitrogen sites in ZJU-40a have nearly no effect on the CO2 uptake, so ZJU-40a adsorbs a similar amount of CO2 (87 cm3 g–1) compared with NOTT-101a (84 cm3 g–1) at 298 K and 1 bar. As a result, ZJU-40a shows significantly enhanced adsorption selectivity for C2H2/CO2 separation (17–11.5) at ambient temperature compared to that of NOTT-101a (8–9), leading to a superior MOF material for highly selective C2H2/CO2 separation.