Naphthalenediimide-Based Metal–Organic Framework with Rare Heterometallic Clusters and Applications in Photocatalysis and Inkless and Erasable Printing

Abstract The electron-deficient 1,4,5,8-naphthalenediimide (NDI) unit serves as a privileged linker for constructing functional metal–organic frameworks (MOFs) with applications in photocatalysis, sensing, and optical information storage. However, the structural and functional tunability of NDI-based MOFs has been intrinsically constrained by the exclusive reliance on single-metal nodes. Herein, the rare heterometallic MOF, [Sr2Zn4(μ3-O)2(BINDI)(H2BINDI)2(H2O)4(DMF)1.5] (1, H4BINDI = N,N′-bis(5-isophthalic acid)naphthalenediimide, DMF = N,N-dimethylformamide), was synthesized, which features rare trinuclear heterometallic [SrZn2(μ3-O)(RCOO)4(RCOOH)2(H2O)2(DMF)0.75] clusters. The distinctive three-dimensional (3D) framework integrates partially uncoordinated carboxylate groups (−COO–) and photoactive NDI moieties, enabling two distinct functions. The extended 3D network effectively separates adjacent NDI ligands to suppress intermolecular electron transfer, prolonging the lifetime of photogenerated color centers and yielding strong color contrast for inkless and erasable printing. Concurrently, the partially uncoordinated −COO– groups electrostatically preconcentrate cationic dyes, while the NDI units efficiently generate reactive oxygen species (ROS) (•O2–/•OH) under illumination; this synergistic effect drives effective and selective photocatalytic degradation of cationic pollutants. This work demonstrates the rare integration of heterometallic nodes into NDI-based MOF chemistry and establishes a structural design strategy for achieving multifunctional synergy in robust framework materials.