Stable Bimetallic Metal–Organic Framework with Dual-Functional Pyrazolate-Carboxylate Ligand: Rational Construction and C2H2/CO2 Separation

With the guidance of the hard/soft acid/base principle, we adopt a strategy to construct a novel robust metal–organic framework (MOF) by using a dual-functional ligand to coordinate with different types of metal ions in a one-pot reaction through coordination self-selection. A bimetallic MOF, namely BUT-85 (BUT = Beijing University of Technology), has been successfully synthesized with a rationally designed pyrazolate-carboxylate ligand. Its robust [Ni2(OH)­(H2O)2Pz3]n chain (Pz = pyrazolate) with bridging OH–/H2O and pyrazolate groups is reported for the first time. This material shows good chemical stability in water and aqueous solutions with a pH range from 3 to 13. In addition, BUT-85 exhibits preferential adsorption behavior of C2H2 over CO2. It is proposed to be attributed to the abundant exposed bridging OH–/H2O sites in [Ni2(OH)­(H2O)2Pz3]n chains, which is supported by the results of molecular simulations. Column breakthrough experiments further confirm that this MOF can realize efficient C2H2/CO2 separation. This strategy can not only enrich the structural library of MOFs but also optimize their properties and functions for promoting applications.