Ligand-Driven Turn-On Fluorescence in Zn/Cd(II) MOFs: Enhancing Emission via Aggregation-Induced Mechanism.

To explore the influence of flexible auxiliary ligands on the construction of Zn/Cd(II) coordination polymers with the rigid π-conjugated ligand HIDPA (5-(1-oxoisoindolin-2-yl)isophthalic acid), five new compounds were synthesized: [Cd(IDPA)(bpa)(HO)]·2(HO) (), [Cd(IDPA)(bpe)(HO)]·(HO) (), [Zn(IDPA)(bpa)]·5(HO) (), [Zn(IDPA)(bpe)] (), and [Zn(IDPA)(bpp)]·(HO) (). Structural analyses reveal diverse architectures ranging from 2D layers (-) with sql topology ({4·6}) to 3D frameworks: a {4·6·8}{4·6·8} net () and a -type network (). These variations highlight the critical role of auxiliary ligand flexibility in directing topology. Photoluminescence studies show distinct emissions (violet to green) under UV light. Notably, compound exhibits an enhanced quantum yield (14.21%) due to aggregation-induced emission (AIE). All compounds display excellent structural stability upon solvent removal. This study demonstrates that combining flexible auxiliary ligands with rigid π-conjugated linkers offers an effective strategy to tune both framework structures and luminescent properties, facilitating the design of functional luminescent materials.