Metal-organic framework sensors based on triazole carboxylic acid ligands for ion sensing and dye adsorption

Three novel metal-organic frameworks (MOFs) [Cd(L)(Ata)(H 2 O)]·H 2 O( 1 )、[Cd 2 (L) 2 (Bda)(NO 3 − )H 2 O]·2H 2 O( 2 ) and [Cd 2 (L) 2 (Tpa) 0.5 (NO 3 − )(H 2 O) 3 ]( 3 ) (Ata ​= ​2-aminoterephthalic acid; Bda ​= ​Succinic acid; Tpa ​= ​Terephthalic acid) were synthesized by reactions of cadmium(II) salt with organic ligands of 3, 5-bis-(triazol-1-yl)-benzoic acid (HL) and 2-aminoterephthalic acid, succinic acid, and terephthalic acid. The crystal structure test revealed that they are three different complexes. Among them, complex 1 is connected by auxiliary ligands to form a two-dimensional layered structure, and complexes 2 and 3 are connected by auxiliary ligands to form a high-dimensional three-dimensional framework structure. Solid-state fluorescence experiments showed that complexes 1 and 2 have excellent optical properties: Complex 1 can selectively detect Cu 2+ (LOD: 1.97 ​μM) and MnO 4 − (LOD: 1.12 ​μM), and complex 2 can selectively detect Fe 3+ (LOD: 1.99 ​μM) and MnO 4 − (LOD: 4.70 ​μM). Amino acid and antibiotic sensing experiments showed that: complex 1 can detect arginine by fluorescence enhancement effect (LOD: 5.40 ​μM), and tetracycline hydrochloride can be detected by quenching effect (LOD: 0.43 ​μM); complex 2 can be detected tryptophan (LOD: 5.72 ​μM) and tetracycline hydrochloride (LOD: 0.63 ​μM). • Complex 1 can selectively detect Cu 2+ , MnO 4 − , ​arginine and tetracycline hydrochloride. • Complex 2 can selectively detect Fe 3+ , ​MnO 4 − , ​tryptophan and tetracycline hydrochloride. • The adsorption efficiencies of complexes 1-3 for CR were 42.69%, 42.76% and 39.71%, respectively.