Adsorbents based on CuI for p-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 CuII to CuI along with aggregation, and (ii) poor stability due to the oxidation of CuI to inactive CuII. 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 CuI 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. (c) 2020 Elsevier Inc. All rights reserved.