Effects of pore size distribution of activated carbon (AC) on CuCl dispersion and CO adsorption for CuCl/AC adsorbent

Cu(I) adsorbents have high adsorption capacity and high selectivity for CO, thanks to the strong π-complexation bonds formed between CO and Cu(I) ions. It is important that the porous support for making Cu(I) adsorbents should have high surface area, however, the effect of pore size has never been reported. In the current study, Cu(I) adsorbents were prepared by impregnating activated carbons (ACs) with Cu(II) chloride and Cu(II) carboxylate, followed by heat treatment at mild condition in vacuum to get highly dispersed CuCl/AC adsorbents. Four ACs with different pore size distribution were studied as the supports for making CuCl/AC adsorbents. The pore size distribution characterized by Ar adsorption at 87 K was defined as ultramicropore (<0.7 nm), supermicropore (0.7–2 nm), small mesopore (2–2.5 nm) and large mesopore (2.5–50 nm). It was found that ultramicropores loaded with CuCl (d = 0.462 nm) did not leave enough space for the accommodation of CO molecules (d = 0.376 nm), resulting in low CO adsorption; large mesopores had large enough pore size for CuCl loading but low surface area for the dispersion of CuCl, leading to low CO adsorption as well. By contrast, supermicropores and small mesopores gave high surface area and suitable pore size for well dispersion of CuCl and enough space for CO adsorption, which makes ACs with mainly supermicropores and small mesopores perfect supports for making robust CO adsorbents.