Chiral lanthanide–silver(i) cluster-based metal–organic frameworks exhibiting solvent stability, and tunable photoluminescence

Abstract

Due to the lack of effective synthetic strategies, the preparation of chemically stable chiral Ag(I) cluster-based materials for assembly remains challenging. Here, we have developed an approach to synthesize three pairs of chiral Ln–Ag(I) cluster-based metal–organic frameworks (MOFs) named L-LnAg₅-3D (Ln = Gd for 1-L, Eu for 2-L, and Tb for 3-L) and D-LnAg₅-3D (Ln = Gd for 1-D, Eu for 2-D, and Tb for 3-D) by employing a chiral Ag(I) cluster ({Ag₅S₆}) as the node and Ln³⁺ ion as the inorganic linker. Structural analysis revealed that the chiral ligands induced chirality through the entire structure, resulting in a chiral helix arrangement of the C₃-symmetric chiral {Ag₅S₆} nodes and Ln³⁺ ions. These compounds showed high solvent stability in various polar organic solvents. The solid-state circular dichroism (CD) spectra of compounds L-LnAg₅-3D and D-LnAg₅-3D exhibited obvious mirror symmetrical peaks. The emission spectra in the solid state revealed that compound 1-L only exhibited the emission peak of {Ag₅S₆}, while compounds 2-L and 3-L exhibited overlapping peaks of Ln³⁺ and {Ag₅S₆} at different excitation wavelengths. This demonstrates the tunable photoluminescence from {Ag₅S₆} to Ln³⁺ by introducing different Ln³⁺ ions and manipulating the excitation wavelengths. The study underscores the enhanced stability of Ag(I) cluster-based MOFs achieved through the incorporation of Ln³⁺ ions and establishes chiral Ln–Ag(I) cluster-based MOFs as promising candidates for advanced materials with tunable photoluminescence.