Ionothermal Syntheses and Characterization of Two Layered Copper/Silver Iodoplumbates Exhibiting Visible-Light Photocurrent Response

Abstract

Organic–inorganic hybrid iodoplumbates have garnered attention due to their diverse structures and optoelectronic properties, showing potential for applications in photoelectric devices and energy conversion. Conventional synthesis methods often involve toxic or volatile organic solvents. In this study, two layered Pb-M (M = Cu, Ag) heterometallic iodoplumbates were successfully synthesized by ionothermal method using iodine-containing ionic liquid as solvent and structure-directing agent, namely (Bmim)(P4442)CuPb6I15 (1) and (Bmim)4/3Ag2/3Pb2I6 (2). Structural analyses reveal that compound 1 features a two-dimensional anionic layer constructed from interconnected [CuI4] tetrahedra and [PbI6] octahedra, exhibiting a unique hexagonal channel architecture. In contrast, compound 2 displays a zigzag layered structure composed of distorted [PbI6] octahedra and partially occupied Ag sites (occupancy = 0.667), which generate an average [AgI4]-based dimeric motif within the inorganic framework. SEM and XPS analyses further confirmed that the heterometallic ions in both compounds are uniformly distributed within the crystal frameworks and exist as Cu+ and Ag+, respectively. Both compounds exhibit good photocurrent response and stability, with the photocurrent density of compound 1 being superior to most reported iodoplumbate complexes. Theoretical calculations revealed its electronic structure and band characteristics. This work not only expands the application of ionic liquids in the synthesis of functional materials, but also provides new insights for designing promising two-dimensional optoelectronic materials.