Mixed‐Valence Coordination Strategy Creating Ordered Ternary Ultrasmall Homo‐/Hetero‐structures Driven by Lattice Match for Advanced Photochromism and Encryption Applications

Abstract Overcoming the challenges of integrating disparate components in nanoarchitectures, this study introduces a straightforward strategy based on a mixed‐valence coordination approach, creating an ordered ternary heterostructure integrated with ultrasmall homojunction. This singular ordered homojunction‐heterostructure unites ultrathin 1D rutile TiO₂ nanowires (NWs) and ultrathin anatase TiO₂ NWs with 0D Prussian Blue Analogs (PBAs) nanoparticles (NPs), all exhibiting crystallographic oriented alignment with each other, forming a ternary mesocrystals. Experimental and theoretical insights disclose that the complex interplay between these dissimilar components is governed by a spontaneous lattice match effect, which not only optimizes but also directs the charge transfer, thereby enhancing both efficiency and stability. It also allows for tailoring the valence states of Fe within the PBA, fine‐tuning of the composite's photochromic properties, and introducing abundant defect structures that foster strong interaction with oxygen molecules, enabling controllable color‐switching dynamics. Consequently, the Fe^II_1−xFe^III_x‐PBA/TiO₂ exhibits an optimized ternary structure of R‐TiO₂/A‐TiO₂/PBA, demonstrating exceptional photoelectronic properties, significantly enhancing photochromism and secure encryption capabilities. These insights establish a solid foundation for engineering sophisticated complex‐ordered nanoarchitectures, advancing sustainable energy and environmental technologies.