Chelating Cu-N within Cu+-incorporated MIL-101 (Cr)-NH2 framework for enhanced CO adsorption and CO/CO2 selectivity

Abstract

The development of π-complexation adsorbents with Cu(I) having high CO adsorption capacity, high selectivity, large working capacity, and good stability is still very challenging up to now. In this work, π-complexation adsorbent with Cu+ was fabricated by reducing Cu2+ to Cu+ within amino-functionalized MIL-101 (Cr) framework by employing formate (HCOO-) at low temperature. The obtained results indicated that the Cu+ yield was strongly influenced by the chelation of Cu(II) species into amino groups (NH2) of MIL-101 (Cr)-NH2. The produced CuCl@MIL-101(Cr)-NH2 (CuCl@MCrN) was then applied for CO and CO2 adsorption at various conditions. The results revealed that the formed Cu+ species within MIL-101 (Cr)-NH2 not only increased CO adsorption via CO π-complexation but also reduced CO2 adsorption on the adsorbent through interaction with NH2 groups, resulting in a significant increase of CO/CO2 selectivity onto CuCl@MCrN adsorbent. At 25 °C and 100 kPa, the prepared CuCl@MCrN adsorbent with 30% Cu(I) exhibited the maximum CO uptake amount and CO/CO2 selectivity of ~ 2.52 mmol g−1 and ~ 97, respectively, exceeding those of the benchmark Cu+-based π-complexation adsorbents. The breakthrough experiment indicates that this Cu(I)@MIL-101(Cr)-NH2 adsorbent can efficiently separate CO/CO2mixture under dynamic mixture flow conditions. Moreover, the oxygen-resistant ability of the adsorbent tested under atmospheric humidity conditions demonstrated that CuCl@MCrN adsorbent had good stability.