The increase in greenhouse gas concentrations has intensified the impact of global warming. Oyster shell (OS) as a source of CaCO₃ has been considered as one of the methods to reduce CO₂, which is one of the primary contributors to global warming. Among various approaches, the adsorption method has proven to be quite effective in reducing CO₂ emissions. This study aims to produce an adsorbent from oyster shells impregnated with metal nitrates that is selective for CO₂ gas. The adsorbent preparation was carried out using the Successive Incipient Wetness Impregnation (SIWI) method, with the material formulation calculated based on stoichiometric ratios. The concentration of metal nitrates used was 2.5%wt (for both aluminum and magnesium metal oxides). The resulting adsorbent was characterized using SEM-EDS (morphology) indicate Al and Mg have been impregnated in oyster shells with 0.5% each. CO₂ capture/adsorption was measured using TGA and found OS/Al exhibited the highest weight loss (5%). Therefore, aluminum nitrate impregnation (OS/Al 5’) is the most effective approach for enhancing the CO₂ adsorption capacity of oyster shells.