Alcohol-assisted hydrothermal synthesis of facet-engineered MgO: Molecular structure effects on CO2 adsorption at high temperature

High-temperature CO₂ capture is vital for hydrogen production and carbon-neutral energy systems. Magnesium oxide (MgO) offers excellent thermal stability and strong Lewis basicity, but controlling the formation of its active (111) plane remains challenging. Here, a one-pot alcohol-assisted hydrothermal method was developed to synthesize MgO nanosheets with highly exposed (111) facets without toxic surfactants or complex procedures. Systematic studies of various alcohols revealed that alcohol-mediated growth effectively promotes (111) plane exposure and strengthens surface basicity, as confirmed by CO₂-TPD and XPS. The optimized MgO showed superior CO₂ adsorption capacities of 1.32 mmol g −1 at 300 °C and 0.44 mmol g −1 at 600 °C, outperforming commercial MgO. DFT calculations indicated that alcohol molecules guide Mg(OH)₂ crystal growth via preferential adsorption, enabling controlled (111) plane formation. This work provides a sustainable and scalable strategy for developing MgO-based CO₂ adsorbents and advances understanding of alcohol-mediated crystal growth. • A green, one-pot alcohol-assisted hydrothermal method was developed for MgO synthesis. • Alcohol molecular structure directs Mg(OH)₂ crystal growth and MgO(111) facet exposure. • Ethanol-assisted MgO shows superior CO₂ uptake (1.32 mmol g −1 at 300 °C, 0.44 at 600 °C). • Provides a scalable route and mechanistic insight for high-temperature CO₂ capture.