| Abstract Scope |
Topochemical modification of anion sublattices in Ruddlesden−Popper (RP) oxides offers a versatile route to tune structure and properties while preserving the parent framework. This lecture focuses on low-temperature reactions in indates, titanates, and mixed B-site systems to understand structure–optical–property relationships for photocatalytic hydrogen evolution. Using polymer-based fluorination (PVDF/PTFE) and hydride reagents (NaH, CaH2), reversible anion exchange is achieved at low temperature. Fluorination of LaBaInO4 to LaBaInO3F2 leads to anisotropic lattice expansion, symmetry changes, and enhanced optical absorption, improving photocatalytic activity, while hydride treatment enables partial defluorination and mixed-anion phases. In a representative mixed B-site indium–antimonate system, Ba2In0.5Sb0.5O4, the presence of Sb is expected to introduce additional redox flexibility and possible lone-pair effects, influencing the structural response during fluorination and reduction compared to pure indium systems. This low-temperature topochemical strategy provides a pathway to design metastable materials with tunable optical and photocatalytic properties. |