ABSTRACT Alkaline metal oxides are promising sorbents for CO 2 capture, yet their performance is often limited by the low density of active sites and poor cyclic stability. Here, we report a nanoclay‐mediated crystal‐facet engineering strategy that simultaneously enhances both CO 2 adsorption capacity and cyclic stability of MgO. Kaolinite acts as a facet‐directing mediator that promotes the preferential exposure of MgO (220) facets enriched with low‐coordinated oxygen step sites (O 4c step), thereby enhancing CO 2 adsorption. The optimized kaolinite‐MgO (K‐M) composite achieves a CO 2 uptake of 0.45 g/g, representing an 11% improvement over pristine MgO, and retains 53% of its capacity after 100 cycles, compared with 26% for MgO. Mechanistic studies combining in situ FTIR spectroscopy and density functional theory calculations reveal that kaolinite simultaneously promotes (220) facet formation and suppresses MgO sintering through the in situ generation of MgSiO 3 . In addition, kilogram‐scale synthesis and binder‐free granulation demonstrate the scalability and engineering applicability of the material. This work provides a scalable, sustainable pathway for designing next‐generation CO 2 capture materials with superior performance and stability.
Liao et al. (Tue,) studied this question.