Ceria and nitrogen decorated Ca-BTC-derived carbon with residual CaO for CO₂ adsorption

Calcium oxide (CaO) is a high-temperature CO₂ capture sorbent. However, it suffers from CaO aggregation for CO₂ scrubbing after looping cycles. To disperse and secure CaO, in this research, we pyrolyzed Ca-based metal-organic frameworks (MOFs) Ca-BTC for CaO on MOF-derived carbon (MDC). Furthermore, ceria or nitrogen was introduced into Ca-MDC by Ce²⁺ or DABA ligand addition to Ca-BTC. Compared to pure CaO, Ca-MDC maintained 30 % better CO₂ adsorption stability after 10 cycles. In comparison, the CO₂ uptake of CeO₂-decorated Ca-MDC kept at about 100 % after 10 cycles, which could be attributed to oxygen vacancy in CeO₂. The highest CO₂ adsorption reached 17.10 mmol/g in N-doped Ca-MDC with 80 % stability. All CaO on MDC samples had CO₂ adsorption exceeding the theoretical stoichiometric ratio 1:1 of CaO:CO₂, implying plausible CO₂ spillover from CaO to carbon matrix. For kinetics analyses, the pseudo-second order (PSO) model showed a better fit than the linear driving force (LDF) model, suggesting strong chemisorption in CaO as expected. The double exponential (DE) model was applied to differentiate CO₂ chemisorption and surface diffusion and showed much higher diffusion rate constants in Ca-MDC than CaO, suggesting a possible CO₂ spillover phenomenon.