The discovery of new structures is very important for metal-organic framework (MOF) adsorbents and their application in gas separation, where the design of ligands and the selection of metal ions play a decisive role. Herein, we synthesized two isoreticular Zn-MOFs, UPC-250 and UPC-251, composed of imidazole-based tricarboxylic acid ligands and binuclear zinc clusters. The pore environment was regulated via modifying fluorine atoms at different positions of ligands, and one-step purification of ethylene from acetylene/ethylene/ethane ternary mixture was realized in UPC-251.