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

Abstract

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.