Separation of ethane from ethylene is a very important but challenging process in the petrochemical industry. Finding an alternative method would reduce the energy needed to make 170 million tons of ethylene manufactured worldwide each year. Adsorptive separation using C2H6-selective porous materials to directly produce high-purity C2H4 is more energy-efficient. We herein report the "reversed C2H6/C2H4 adsorption" in a metal-organic framework Cr-Bit via the introduction of oxygen on its open metal sites. The oxidized Cr-BTC(O-2) can bind C2H6 over C2H4 through the active Cr-superoxo sites, which was elucidated by the gas sorption isotherms and density functional theory calculations. This material thus exhibits a good performance for the separation of 50/50 C2H6/C2H4 mixtures to produce 99.99% pure C2H4 in a single separation operation. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.