Dinitrogen‐containing five‐membered heterocyclic porous liquids for selective separation of 1,3‐butadiene

Abstract 1,3‐Butadiene is an essential monomer in the production of synthetic rubbers and high‐value polymers. However, separating it from C4 mixtures is extremely difficult due to the similar physicochemical properties of C4 olefins. A novel porous liquid (PL) has been designed that combines Mn‐bpdc MOF as the porous host and a dinitrogen‐containing five‐membered, heterocyclic DES (2EmimCl:CH 3 ‐Im) as the steric hindrance solvent. The Mn‐bpdc provides one‐dimensional channels with precise molecular sieving and gate‐opening behavior toward 1,3‐butadiene. The dual imidazole rings form strong π–π interactions with 1,3‐butadiene, and Cl − enhances affinity via the inductive effect. At 5 wt% Mn‐bpdc loading, the PL's selectivity for 1,3‐butadiene/1‐butene increased from 9.20 to 17.21, with excellent cyclic stability over five cycles. Quantum calculations reveal that the PL interacts with 1,3‐butadiene via a synergistic effect of hydrogen bonds, π–π stacking, dispersion, and electrostatic forces. The synergy between specific intermolecular forces and size exclusion enables highly efficient separation of 1,3‐butadiene.