NaNO2-loaded mesoporous MgO for high-efficiency CO2 capture: Synthesis, characterization and novel mechanistic insights

• NaNO2-modified mesoporous MgO achieves a high CO2 adsorption capacity of 12.6 mmol/g at 325 °C under pure CO2. • The modification induces formation of NaNO3 and Na2CO3, which synergistically enhance oxygen vacancies and nucleation sites. • The adsorption mechanism involves MgCO3 formation and subsequent conversion to Na2Mg(CO3)2, with kinetics governed by surface reaction and diffusion. • The study provides mechanistic insights for rational design of advanced MgO-based CO2 adsorbents.