Typical amorphous aerogels pose great potential for CO2 adsorbents with high surface areas and facile diffusion, but they lack well-defined porosity and specific selectivity, inhibiting utilization of their full functionality. To assign well-defined porous structures to aerogels, a hierarchical metal-organic aerogel (HMOA) is designed, which consists of well-defined micropores (d ∼ 1 nm) by coordinative integration with chromium(III) and organic ligands. Due to its hierarchical structure with intrinsically flexible coordination, the HMOA has excellent porous features of a high surface area and a reusable surface with appropriate binding energy for CO2 adsorption. The HMOA features high CO2 adsorption capacity, high CO2/N2 IAST selectivity, and vacuum-induced surface regenerability (100% through 20 cycles). Further, the HMOA could be prepared via simple ambient drying methods while retaining the microporous network. This unique surface-tension-resistant micropore formation and flexible coordination systems of HMOA make it a potential candidate for a CO2 adsorbent with industrial scalability and reproducibility.
Keywords: gas selectivity; hierarchical metal−organic aerogel; metal−organic gel; microporous materials; paddle-wheel structure; reusable CO2 adsorbents.