Functional analysis of heteroatom-doped carbon materials for effective trace CO adsorption

CO adsorbent production from carbonaceous sources remains challenging in developing straightforward synthesis strategies for functional carbon materials that enhance CO-selective adsorption and oxidation resistance of Cu1+ ions. We synthesized different heteroatom-doped carbon supports by a simple pyrolysis method, employing carbon, nitrogen, and boron atom precursors to modify Cu1+ ion's adsorptive characteristics for CO. The CN ligands from N-doped carbon improved dispersion and stabilization of 30 wt% Cu1+ ions, impregnated from CuCl solution. This led to high CO adsorption uptake -33 cm3/g at 100 kPa with 86 % adsorption stability after 30day air exposure. Unexpectedly, even after being impregnated with 30 wt% Cu1+ ions, N-doped carbon still occupied extra free N-sites with CO2-affinity, resulting in inferior CO/CO2 adsorption selectivity -1.1 at 100 kPa. To address this, B, N-co-doped carbon with increased surface acidity was investigated as CO2-repellent support for improving CO-selective adsorption without overuse of costly CuCl. With the fixed 30 wt% Cu1+-impregnation, additional B loading as 5 wt% on N-doped carbon raised CO/CO2 selectivity from 1.1 to 2.6 at 100 kPa via acid-acid repulsion between CO2 and B-species. This co-doping effect was remarkable in low-pressure adsorption, highly improving CO/CO2 selectivity to 79 at 0.4 kPa for effective trace CO capture.