Guest-Induced Mutation of a Local Coordinative Structure in M-Gallate Metal–Organic Frameworks for Selective Adsorption of Ethylene from Ethane

Abstract

In order to achieve efficient separation of ethylene/ethane systems, the ethylene industry urgently needs efficient adsorbents. The combination of advantages of ultra-microporous restriction and strong affinity from open adsorption sites is expected to achieve highly selective adsorption of ethylene. Herein, we systematically and deeply investigate the gas adsorption behavior of M-gallate series metal−organic framework materials (M = Co, Ni, and Mg). Combined with experimental results such as in situ diffuse reflectance infrared Fourier transform and density functional theory calculation, we successfully proposed an ethylene gas adsorption mechanism based on the local coordinative structure mutation induced by guest molecules. This mechanism suggests that when ethylene molecules are adsorbed, the electronic donor property of π electrons and the d−π feedback effect lead to a shift of the flexible phenolic hydroxyl group and spin state transitions of Co in Co-gallate, thereby exposing the Co site and enhancing the strong affinity to ethylene. The proposed mechanism provides an inspiration and theoretical basis for the subsequent development of efficient selective adsorbents for the separation of ethylene and ethane.