Confinement of Ag(I) sites within MIL-101 for robust ethylene/ethane separation

Effective utilization of Ag(I) π-complexation adsorbents for practical C2H4/C2H6 separation urges both good separating performances and high stabilities. In this work, we incorporated AgNO3 onto a typical metal-organic framework (MOF) of MIL-101 to obtain efficient Ag(I) π-complexation adsorbents. It was found that the separation performances were highly dependent on the location of the AgNO3, which could be at the interior or the exterior of nanoporous MIL-101. Confining AgNO3 inside the nanopores of MIL-101 was achieved through employing a double-solvent approach. The resulting AgM-DS adsorbents exhibited superior performances compared with not only pristine MIL-101 but also other modified samples with AgNO3 at the exterior of MIL-101. To be specific, the optimal 1.6AgM-DS adsorbent secured good C2H4/C2H6 separation, which is C2H4 uptake (75.5 cm3·g-1) and C2H4/C2H6 selectivity (9.5) at 100 kPa. For comparison, the C2H4 uptakes for MIL-101, 1.6AgM-WI, and 1.6AgM-SG were merely 48.1, 56.0, and 19.4 cm3·g-1, and the corresponding IAST selectivity was only 1.1, 8.1, and 1.8, respectively. It was further indicated that the 1.6AgM-DS adsorbent maintained good stability for 3 weeks, alleviating the light sensitivity of AgNO3. This work opens an avenue for constructing stable Ag(I) sites on MOFs to develop π-complexation adsorbents.