Pillar-Layered strategy to design and synthesis of two MOFs with excellent C₂H₂ capture and C₂H₂/CO₂ separation capability

Acetylene and carbon dioxide share similar physical properties, which poses a significant challenge for their industrial separation. Therefore, it is crucial to design and synthesize specific physical adsorbents for this purpose. In this study, two pcu topological MOFs materials named JLU-MOF102 {[Ni(HPyC)2(BPY)] (DMF)2(H2O)2} and JLU-MOF103 {[Ni(HPyC)2(PYZ)] (H2O)2} (4-pyrazolecarboxylic acid = H2PyC, 4,4 ' bipyridine = BPY, pyrazine = PYZ, DMF = N, N- dimethylformamide), were successfully synthesized to facilitate the separation of C2H2 and CO2. These MOFs were synthesized by using the pillar-layered strategy, both having the same sql layer (combined Ni2+ and HPYC) but different pillar ligands (BPY for JLU-MOF102 and PYZ for JLU-MOF103, respectively). The pore size of JLU-MOF103 is smaller than that of JLU-MOF102 and the interaction between JLU-MOF103 and C2H2 molecules is stronger. JLU-MOF102 and JLU-MOF103 exhibit significant ability to capture C2H2 (125.8 and 96.7 cm3/g, respectively) and the selectivity for C2H2/CO2 (v/v = 50/50) mixture is 4.5 and 14.0 calculated by IAST, respectively, at 298 K and 1 bar. First-principles-based calculations reveal subtle differences in host-guest interactions between JLU-MOF102 and JLU-MOF103 originated from the porous structures, which account for their distinct separation selectivity. The dynamic column breakthrough experiments demonstrated that JLU-MOF103 had a higher C2H2 adsorption capacity of 2.01 mmol/g compared to JLU-MOF102 (1.16 mmol/g). The low cost, excellent stability and good recycling ability suggest the potential of JLU-MOF103 for industrial applications.