Biomimetic Confined Crystallization of Large-Sized Single-Crystalline Multicomponent Mesoporous Metal Oxides

The performance of mesoporous metal oxides (MMOs) depends strongly on the composition, crystallinity, and size. However, soft-templating synthesis of multicomponent systems is typically constrained by poor structural control arising from phase separation, uncontrolled nucleation, and structural collapse. Inspired by biomineralization, this study proposes a biomimetic confined crystallization strategy based on constructing a 3D continuous poly(acrylic acid) matrix. This matrix forms a flexible organic-inorganic network that stabilizes intermediate species, regulates crystallization kinetics, suppresses burst nucleation, and promotes integrated crystal growth, thereby playing a role analogous to the organic framework in natural biomineralization. In addition, the template directs mesostructure formation through its space-occupying effect and decomposition-induced gas evolution. As a result, large-sized single-crystalline multicomponent MMOs were successfully synthesized. More importantly, this strategy enables precise and tunable control of crystallinity and particle size and can be readily extended to more than ten multicomponent systems. As a representative example, La₂FeCuO₆ exhibits a Faradaic efficiency of 98.2% for electrocatalytic nitrate reduction, benefiting from the synergistic effects of optimized electronic structure, mesoporosity, and single crystallinity. Overall, this work establishes a biomimetic route to overcome the intrinsic limitations of conventional soft-templating approaches, particularly phase separation, polycrystallization, and the difficulty of achieving large-sized crystal growth under high-temperature calcination.