Encapsulation of cuprous/cobalt sites in metal organic framework for enhanced C₂H₄/C₂H₆ separation

Adsorbents based on Cu^I for π-complexative separation of C₂H₄/C₂H₆ 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^II to Cu^I along with aggregation, and (ii) poor stability due to the oxidation of Cu^I to inactive Cu^II. 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^I without any structural damage to MIL-101. The resulting CuCoM-DS exhibits a superior performance in C₂H₄/C₂H₆ 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^-1 of C₂H₄, and the C₂H₄/C₂H₆ selectivity is 2.6 at 100 kPa. Both C₂H₄ uptake and C₂H₄/C₂H₆ selectivity are higher than those reference samples. Moreover, 1.5CuCoM-DS preserves over 90% of fresh C₂H₄ 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.