Self-Assembled Core-Shell Structure MgO@TiO₂ as a K₂CO₃ Support with Superior Performance for Direct Air Capture CO₂

Traditional carbon capture and storage technologies for large point sources can at best slow the rate of increase in atmospheric CO₂ concentrations. In contrast, direct capture of CO₂ from ambient air, or "direct air capture" (DAC), offers the potential to become a truly carbon-negative technology. Composite solid adsorbents fabricated by impregnating a porous matrix with K₂CO₃ are promising adsorbents for the adsorption capture of CO₂ from ambient air. Nevertheless, the adsorbent can be rapidly deactivated during continuous adsorption/desorption cycles. In this study, MgO-supported, TiO₂-stabilized MgO@TiO₂ core-shell structures were prepared as supports using a novel self-assembled (SA) method and then impregnated with 50 wt % K₂CO₃ (K₂CO₃/MgO@TiO₂, denoted as SA-KM@T). The adsorbent exhibits a high CO₂ capture capacity of ∼126.6 mg CO₂/g sorbent in direct air adsorption and maintained a performance of 20 adsorption/desorption cycles at 300 °C mid-temperature, which was much better than that of K₂CO₃/MgO. Analysis proved that the core-shell structure of the support effectively inhibited the reaction between the active component (K₂CO₃) and the main support (MgO) by the addition of TiO₂, resulting in higher reactivity, thermal stability, and antiagglomeration properties. This work provides an alternative strategy for DAC applications using adsorbents.