Molten Salt Template Synthesis of Hierarchical Porous Nitrogen-Containing Activated Carbon Derived from Chitosan for CO2 Capture

Here, hierarchical porous nitrogen-containing activated carbons (N-ACs) were prepared with LiCl-ZnCl2 molten salt as a template derived from cheap chitosan via simple one-step carbonization. The obtained N-ACs with the highest specific surface area of 2025 m2 g–1 and a high nitrogen content of 5.1 wt % were obtained using low molten salt/chitosan mass ratio (3/1) and moderate calcination temperature (1000 °C). Importantly, using these N-ACs as CO2 solid-state adsorbents, the maximum CO2 capture capacities could be up to 7.9/5.6 mmol g–1 at 0 °C/25 °C under 1 bar pressure, respectively. These CO2 capture capacities of N-ACs were the highest compared to reported biomass-derived carbon materials, and these values were also comparable to most of porous carbon materials. Moreover, as-made N-ACs also showed good selectivity for CO2/N2 separation and excellent recyclability. The unique hierarchical porous structure of N-ACs thus provided the right combination of adsorbent properties and could enable the design of high-performance CO2 solid adsorbents.