Nitrogen-doped porous aromatic frameworks for enhanced CO2 adsorption.

Recently synthesized porous aromatic frameworks (PAFs) exhibit extremely high surface areas and exceptional thermal and hydrothermal stabilities. Using computer-aided design, we propose new PAFs, designated as NPAFs, by introducing nitrogen-containing groups to the biphenyl unit and predict their CO2 adsorption capacities with grand canonical Monte Carlo (GCMC) simulations. Among various NPAFs considered, one with imidazole groups shows the highest adsorption capacity for CO2 (11.5 wt% at 1 bar and 298 K), in comparison with 5 wt% for the parent PAF (PAF-1) at the same condition. At higher pressures (around 10 bar), however, another NPAF with pyridinic N groups performs much better than the rest due to its greater pore volume in addition to the N functionality. This study suggests that adding N functionality to the organic linkers is a promising way to increase CO2 adsorption capacity of PAFs at ambient condition.