A novel approach to prepare Cu(I)Zn@MIL-100(Fe) adsorbent with high CO adsorption capacity, CO/CO2 selectivity and stability via controlled host-guest redox reaction

The development of a CO-selective adsorbent with large CO adsorption capacity, high CO/CO2 selectivity, and good stability is an industrial challenge. In this study, a novel Cu(I)-incorporated MIL-100(Fe) adsorbent for CO/CO2 separation is prepared using a host-guest redox strategy by exploiting the co-addition of Zn(II) and Cu(II). The addition of Zn(II) resulted in a higher Cu(I) yield of the adsorbent due to the facilitated regeneration of Fe (II), which was utilized for the reduction of Cu(II). Remarkably, the CO/CO2 selectivity (104) of Cu(I)Zn@MIL-100(Fe)-10 was considerably higher than that of the benchmark Cu(I)-incorporated adsorbents. Increasing the Zn(II) concentration in Cu(I)Zn@MIL-100(Fe)-10 improved the oxygen resistance. Density functional theory calculations support our hypothesis that the above improvements are derived from stronger sigma-bonding between Cu(I) and CO and the facilitation of Fe(II) regeneration by the addition of Zn(II). This study opens a new perspective for developing efficient CO-selective pi-complexation adsorbents with high CO/CO2 selectivity and superior oxygen resistance.