Insights into the post-combustion CO2 capture performance of zinc-based zeolitic imidazolate framework (ZIF8)-derived nanocomposites

We report carbon-zinc oxide (C/ZnO) nanocomposites obtained by a simple, scalable, and cost-effective one-step pyrolysis of a zinc-based zeolitic imidazolate framework (ZIF8) for post-combustion carbon dioxide (CO₂) capture. The prepared nanocomposites are thoroughly analyzed by different characterization techniques. The CO₂ adsorption–desorption studies performed using thermogravimetric analyzer (TGA) reveal remarkable CO₂ adsorption capacity (∼10 wt% at 30 °C, 1 bar) and excellent CO₂/N₂ selectivity. The low-pressure CO₂ uptake capacities measured using Brunauer-Emmett-Teller (BET) analyzer corroborate the TGA results. The best sample exhibits an uptake of 3.13 mmol/g at 30 °C, 1 bar. The experimental isotherms obtained using TGA and BET are fitted using suitable kinetic and adsorption models, respectively, to obtain insights into the underlying adsorption mechanisms. The isosteric enthalpy of adsorption calculated from the Virial analysis of the isotherms confirms the physisorption nature. Excellent CO₂ uptake values are also observed in simulated flue gas environments. Additionally, the factors influencing the CO₂ adsorption in these nanocomposites are identified by correlating the physical characterization results with the CO₂ uptake studies. It is inferred that the amorphous carbon in the nanocomposite determines the adsorption capacity and selectivity, whereas the residual ZnO in it controls the adsorption capacity at 0.15 bar and kinetics.