Coordination environment dependent stability of Cu-based MOFs towards selective adsorption desulfurization

Abstract

Cu-based metal organic frameworks (MOFs) are promising adsorbents for the selective adsorption desulfurization (SADS) towards mercaptans in fossil fuels, while the structural collapse problem restricts their application due to the strong interaction between the copper cations and mercaptans. To find a solution, the factors mattering to the SADS ability of MOFs are comprehensively discussed by comparing the structure–activity relationship of 16 MOFs. Especially, the influence of topology, structure of second building unit (SBU) and coordination environment of metal cations of these MOFs are investigated. The experimental results indicate that the binding strength between copper cations and mercaptan is mainly dependent by the coordination environment of the copper cations. And a MOF, ADODAA with copper cations squarely coordinated with two oxygen and two nitrogen atoms exhibits significantly higher stability and renewability over other Cu-based MOFs whose copper cations only coordinates with four oxygen or nitrogen atoms, due to its moderate binding strength towards mercaptan. This work unravels the strong dependence of the stability of MOFs on the coordination environment of its metal cations and provides a platform for constructing highly stable SADS adsorbents.