High-Energy-Facet-Oriented Mesoporous Single-Crystal Metal Oxides for Selective Oxidation Catalysis.

Abstract

Mesoporous single-crystal metal oxides are highly attractive for heterogeneous catalysis because they combine high surface accessibility with long-range lattice coherence; however, their synthesis remains fundamentally challenging due to the thermodynamic incompatibility between crystallization and pore formation. Here we report a template-free, energy-driven facet-oriented crystallization strategy that enables the formation of mesoporous single-crystal metal oxides with tunable pore architectures and exposed high-energy facets. Polyvinylpyrrolidone functions simultaneously as a pore maintainer and surface-energy regulator, preserving mesoporosity while selectively stabilizing high-energy facets to direct single-crystal growth. The method is applicable to multiple oxides, including Co₃O₄, MgO, NiO, and mixed-metal systems. As a representative example, mesoporous single-crystal Co₃O₄ with preferentially exposed (111) facets exhibits outstanding performance in the selective oxidation of aromatic alkanes, achieving up to 99% conversion and selectivity under mild conditions. Experimental and theoretical analyses suggest that the synergy between mesoporosity and active-facet exposure enhances reactant adsorption, oxygen activation, and reaction kinetics, providing a general design principle for crystallographically defined porous catalysts.