Highly regenerable cubic and terraced MgO nanoparticles as CO₂ adsorbents for room-temperature wet mineral...

Mineral carbonation using magnesium oxide (MgO) represents a highly effective pathway for mitigating climate change due to its significant theoretical capacity and environmental safety. To maximize the life-cycle sustainability of this process, the cyclic stability and effective regeneration of MgO adsorbents are critical requirements. In this work, we investigate the repeatability of carbon capture capacities for aerosol-synthesized, high-purity cubic and terraced (C- and T-MgO) nanoparticles through 15 cycles of wet carbonation (WC) at room temperature (∼25 °C) and thermal decarbonation (DC) at 800 °C. Morphological analysis revealed that nano-sized MgO particles were transformed into micro-sized, pillar-shaped magnesium carbonates, primarily artinite and nesquehonite, during the WC phase. Subsequent thermal treatment regenerated the MgO phase, which maintained a porous, pillar-like structure characterized by internal cracks formed during CO₂ release. Pore size distributions stabilized after the initial five cycles, providing permanent diffusion channels that ensure consistent kinetic performance. The persistence of high reactivity was supported by the sustained presence of surface oxygen vacancies and defects, as confirmed by XPS analysis. The C- and T-MgO adsorbents achieved average capture capacities of 21.03 and 21.41 mmol CO2/g adsorbent, respectively, with a remarkably low-capacity loss of less than 4% over 15 cycles. These results approached theoretical limits and significantly outperformed previously reported composite materials modified with dopants. This exceptional stability of aerosol-synthesized MgO based adsorbents can be applied for low-energy direct air capture and flue gas treatment as sustainable carbon management strategies by integrated with industrial waste heat recovery or renewable energy infrastructures.