Dual-Ligand MOFs for Multifunctional Fluorescence Sensing: Selective Detection of Environmental Pollutants and Pharmaceuticals via Turn-On/Off Responses

Three novel 3D metal–organic frameworks (MOFs), [Zn(L)(1,3-pda)]·H 2 O ( MOF 1 ), [Cd(L)(1,3-pda)]·H 2 O ( MOF 2 ), and [Co 3 (L)(1,3-pda) 2 (H 2 O) 4 ] ( MOF 3 ), were solvothermally synthesized using 2,6-bis(1-imidazolyl)naphthalene (L) and 2,2’-(1,3-phenylene)diacetic acid (1,3-H 2 pda) as dual ligands. These MOFs exhibit strong fluorescence and high stability in aqueous environments. Notably, all three MOFs demonstrate selective turn-off sensing toward acetone, Fe 3+, CrO 4 2–, and Cr 2 O 7 2– . Additionally, MOF 1 and MOF 3 show dual-mode fluorescence responses to antibiotics: turn-off for nitrofurazone (NZF) and turn-on for kanamycin sulfate (SKAN). Detailed sensing studies reveal low detection limits (10 –7 M level), high selectivity, and excellent recyclability. The selective recognition properties of the three MOFs toward different analytes were further elucidated through experimental and computational studies. These results highlight the potential of these MOFs as multifunctional fluorescence sensors for environmental and pharmaceutical analysis.