Stepwise structural engineering of coordination polymers via metal and ligand selection enables fluorescent sensing of Ru3+ ions

Precise structural engineering of coordination polymers through rational selection of metal centers and organic ligands is essential for tuning their architectures and properties. Here, three new coordination polymers, [Zn 2 (L1) 2 (L2) 2 ·1DMF] n ( 1 ), [Cd 2 (L1) 2 (L2) 2 ] n ( 2 ), and [Cd 2 (L1) 2 (L3) 3 ] n ( 3 ) (L1 = 4,4′-(anthracene-9,10-diyl)-dibenzoic acid, L2 = 1,4-bis(4-pyridyl)naphthalene, L3 = 9,10-bis(4-pyridyl)anthracene, DMF = N,N -dimethylformamide), were synthesized via solvothermal methods. Single-crystal X-ray diffraction shows that 1 and 2 are isostructural 3-fold interpenetrated frameworks with minor differences induced by the metal centers. The use of the bulkier ligand L3 in compound 3 yields a distinct 3-fold interpenetrated framework structurally related to those of 1 and 2 , stabilized by uncoordinated pyridyl groups through N–H···π interactions, but distinguished by half of the L 3 ligands featuring uncoordinated pyridyl groups that engage in N–H···π interactions to stabilize the structure. Notably, compound 2 exhibits the selectivity and sensitivity for fluorescence turn-off detection of Ru 3+ ions in water, with a detection limit of 3.44 μM. These results demonstrate that both subtle and significant framework modifications can be achieved through stepwise metal and ligand design, providing guidance for developing metal-organic frameworks with optimized ion sensing properties.