A water-stable fcu-MOF material with exposed amino groups for the multi-functional separation of small molecules

Abstract

The energy-efficient purification of methane from C2-hydrocarbons is of great significance for the upgrading of natural gas. So does the capture of carbon dioxide for remission of greenhouse effect. It is well established that some functional sites, such as open metals sites, Lewis basic nitrogen sites and fluorine groups, have shown significantly enhanced affinity toward more polarizable molecules. Thus, a water-stable Eu3+-based fcu-metal-organic framework (MOF) (compound 1) with amino functional groups has been successfully constructed through a reticular chemistry approach. As a result, the activated compound 1 exhibits moderately high uptakes of C2-hydrocarbons, but a less obvious adsorption of CH4 at the same conditions. Among them, the adsorption capacity of C2H2 is up to 143.6 cm3 cm−3 and a relatively high selectivity of C2H2/CH4 (107.7) is obtained at near room temperature. Moreover, compound 1 is also validated as an exceptional adsorbent for CO2 capture, with the fairly high capacity of CO2 (92.6 cm3 cm−3) and CO2/N2 selectivity (151.7) at ambient conditions. The excellent performance of compound 1 is mainly driven by the exposed amino functional groups within the contracted pores. Such effect thus leads to the achievement of dual-functional platform for methane purification and carbon dioxide capture. Furthermore, compound 1 features a satisfactory water stability, which is confirmed by the powder X-ray diffraction (PXRD) analysis and the retest of porosity after being soaked in water.