In Situ Reducible Ionic Frameworks for Dual-Site and Photothermal Catalysis

Ionic frameworks (IFs), characterized by ionic bonds and periodic framework structures, find extensive applications in several fields. However, the inherent high bond energy of ionic bonds often leads to the formation of close-packed structures rather than open frameworks. Consequently, the selection of suitable building units is pivotal for the successful synthesis of IFs. Utilizing the large size and negative charge of polyoxometalates (POMs), along with their combination with metal cations, offers an effective approach for constructing IFs. In this study, 2D IFs are fabricated using {Na₄O₁₈} cluster formed by sodium ions and Anderson-type polyanions. Polyoxovanadates are integrated into the framework voids, resulting in a uniform distribution of the two clusters. The catalytic performance of IFs is evaluated through two reactions, revealing that two clusters IFs act as dual-site catalysts, thereby enhancing reaction efficiency. In the presence of strong reductants, polyoxovanadates undergo partial reduction, inducing a single-crystal-to-single-crystal transformation. The reduced IFs display pronounced photothermal conversion capabilities and serve as efficient photothermal-catalytic agents for the cycloaddition of epoxides and carbon dioxide. This research not only enhances the structural diversity of IFs and achieves uniform cluster distribution but also pioneeringly demonstrates the in situ reduction of IFs and their application in near-infrared photothermal catalysis.