Encapsulation of cuprous/cobalt sites in metal organic framework for enhanced CH/CH separation.

Adsorbents based on Cu for π-complexative separation of CH/CH have attracted widespread interests. However, they are still confronting some challenges, for example, (i) a low separation efficiency, resulted from the ineffective reduction of Cu to Cu along with aggregation, and (ii) poor stability due to the oxidation of Cu to inactive Cu. In this study, active Cu and auxiliary Co species are simultaneously encapsulated within the nanopores of MIL-101 using a double-solvent (DS) method to obtain CuCoM-DS. The Cu species at the interior of MIL-101 are homogeneously dispersed and can be completely reduced to Cu without any structural damage to MIL-101. The resulting CuCoM-DS exhibits a superior performance in CH/CH separation not only to the pristine MIL-101, but to the counterpart samples of single Cu and/or Cu/Co at the exterior of MIL-101. The best sample of 1.5CuCoM-DS adsorbent is capable to adsorb 50.5 mL·g of CH, and the CH/CH selectivity is 2.6 at 100 kPa. Both CH uptake and CH/CH selectivity are higher than those reference samples. Moreover, 1.5CuCoM-DS preserves over 90% of fresh CH uptake after the exposure to atmospheric air for 12 days. This study provides new design ideas for confining bimetallic sites in MOFs for broad applications.