High-quality pure acetylene (C2H2) is a kind of crucial starting material for various value-added products. However, selective capture of C2H2from the main impurity of CO2via porous absorbents is a great challenge, as they possess extremely similar kinetic diameters and boiling points, as well as the explosive and reactive properties of C2H2. Herein, we report a porous coordination polymer (PCP), (NTU-55), which assembled from the coordination between a Cu dimer and a newly designed ligand with a nonmetal selenium (Se) site. Static single-component adsorption and dynamic breakthrough experiments reveal that desolvated NTU-55can completely adsorb C2H2from the C2H2/CO2mixture (1/4, v/v) at 298 K, along with higher C2H2capacity and much lower binding energy. The origin of this separation, as comprehensively revealed by density functional theory (DFT) calculations, is derived from the interaction discriminatory of C2H2and CO2toward accessible Se and Cu adsorption sites. To the best of our knowledge, this is the first time to find the positive effect of nonmetal Se sites for selective C2H2capture.