Solid–solid thermal synthesis of bimetallic Ni/Zn embedded in N-doped porous carbon for efficient adsorptive separation based on CO2 adsorption at low pressure

High-efficient adsorptive materials for carbon dioxide (CO2) capture and separation of a gas mixture are vital for energy consumption and emission reduction but are still a substantial challenge. A facile synthesis of bimetallic nickel/zinc embedded in N-doped carbon (Ni/Zn@NC) through the solid–solid thermal method (SST) is developed herein. The SST method is a straightforward procedure with the advantage that the materials are obtained in a single step and solvent-free conditions. Thermal analysis and material characterization were used to investigate the synthesis mechanism during the SST process. The results revealed that an intermediate material, initially obtained at a low thermal temperature, was sacrificed to generate Ni/Zn@NC at high temperatures of the SST method. The resulting robust carbon structure, decorated with heteroatoms (Ni, Zn, N), exhibits a potential for efficient CO2 adsorption during the capture and separation of biogas (CO2/CH4), off-gas (CO2/N2), and natural gas (CH4/ N2). The synergetic effect of Ni in the materials enhances the selectivity of SCO2/CH4, SCO2/N2, and SCH4/N2. The improved selectivities by effective sites were confirmed by computational modeling. Significantly, the Ni/Zn@NC material obtained through a mild yet simple synthesis method (SST) exhibits substantially higher CO2 adsorption capacity and selectivity when compared to commercial carbon (activated charcoal).