Effective separation of acetylene from carbon dioxide via commensurate adsorption in a microporous metal-organic framework

•The C2H2 molecules are adsorbed in the pore channel of PCN-200 in a commensurate manner.•Dynamic separation of C2H2/CO2 is achieved.•The C2H2 molecule is strongly oriented to the two uncoordinated oxygen atoms on the pore surface with a side-on style. Separating acetylene and carbon dioxide is a significant challenge due to their similar physicochemical properties. Herein, we reported an ultramicroporous metal–organic framework, PCN-200, which possesses narrow zig-zag one-dimensional channels with a size of about 4.5 Å. The pore surface of PCN-200 features numerous uncoordinated oxygen polar sites that are symmetrically distributed, facilitating the strong and commensurate binding of acetylene molecules (57.0 kJ mol−1). At 298 K and 1 bar, PCN-200 demonstrates a high selectivity (6.4) towards acetylene over carbon dioxide, and this separation performance is validated through dynamic breakthrough experiments. Simulation studies were conducted to gain insight into the adsorption mechanism for acetylene and carbon dioxide molecules in PCN-200.