Controlled Construction of Cu(I) Sites within Confined Spaces via Host-Guest Redox: Highly Efficient Adsorbents for Selective CO Adsorption

摘要

Here, we designed a double-solvent/host-guest redox combined strategy to construct Cu+ sites in metal-organic frameworks (MOFs) for the first time. As a proof of concept, a representative MOF MIL-100(Fe) with tunable valence states of cations was employed as the host. The combined strategy realizes selective introduction of Cu2+ precursors to the interior pores of MIL-100(Fe), remarkably minimizing the aggregation of Cu2+ and subsequently formed Cu+ species. Owing to the proper reducibility of in situ formed Fe2+ in the frameworks, controlled conversation of Cu2+ to Cu+ with similar to 100% yield is achieved in the absence of any additional reducing agents. These characteristics make the obtained materials Cu+-modified MIL-100(Fe) highly active in selective CO adsorption. The CO adsorption capacity is up to 3.75 mmol.g(-1) at 298 K and 1 bar, which is superior to all other Cu+-containing adsorbents reported so far such as CuCI/activated carbon (2.5 mmol.g(-1)), CuCl/gamma-Al2O3 (1.0 mmol.g(-1)), and CuCl/SBA-15 (0.50 mmol-g(-1)). The same adsorbent also exhibits quite high selectivity of CO over N-2, and the ideal adsorption solution theory selectivity reaches 424. The outstanding CO adsorption performance make the present adsorbents great potential in separation of CO from various mixtures.