Interfacial Engineering Unlocks Mesoporous Hematite Single Crystals to Boost Catalytic Activity

Abstract Single‐crystalline metal oxides exhibit diverse properties, enabling their broad utilization in optoelectronics, magnetics, and catalysis. Constructing porous structures in metal oxides can further enhance their intrinsic activities by increasing specific surface areas, however, their synthesis is seldom reported due to the fact that the crystallization process typically excludes, rather than includes, soft porogens. Herein, this work reports the synthesis of mesoporous hematite single crystals via a mesocrystal topological transformation strategy. An abnormally high density and thick ligand shell on the surface of primary particles in mesocrystals is enabled by an interfacial molecule engineering. It leads to the inclusion of abundant polymer ligands as porogens in mesocrystals, which can then evolve into mesoporous single crystals with high surface areas after calcination. The mesostructure effectively increases active sites and facilitates molecular transport, while the nanosized and single‐crystalline wall promotes the phase transition for catalysis. As a result, the fabricated mesoporous hematite can impart a doubling CO conversion rate of 60.3% in Fischer‐Tropsch synthesis at 280 °C, compared with the nonporous counterpart.