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.