<p>This study presents a modification strategy involving the introduction of oxygen atoms into the linker of nano-sized Zeolitic Imidazolate Framework-8 (ZIF-8) through the thermal method in order to enhance their CO₂ adsorption capacity. In particular, the thermal oxidation modification influences the CO₂ adsorption capacity of ZIF-8 by incorporating isocyanate groups into organic linkers. Additionally, the impact of temperature and reaction time has negligible effects on surface area and pore structure but significantly alters the surface chemical states, leading to improved CO₂ adsorption. The optimal CO₂ capture observed in C300-T3 as an oxidized ZIF-8 sample is due to the higher oxidation temperature of 300&#xa0;°C for 3&#xa0;h, which creates additional adsorption sites and minimizes structural degradation. In the ambient environment, the CO₂ adsorption capacity of C300-T3 increased substantially by 80.4% compared to pristine ZIF-8. This boost resulted in the capacity increasing from 3.1 to 5.7 mmolCO₂/g. Moreover, it was observed that the CO₂ adsorption capacity of oxidized ZIF-8 samples is directly proportional to the level of oxidation. However, prolonged oxidation could result in the decomposition of ZIF-8, leading to a decrease in CO₂ adsorption. Furthermore, it was found that oxidized ZIF-8 samples maintain a stable CO₂ adsorption capacity even after 5 cycles. These results emphasize the efficacy of thermal oxidation as a straightforward modification strategy for functionalizing ZIF-8 and enhancing their capability for CO₂ capture.</p>