Triazole-Based Cu(I) Cationic Metal-Organic Frameworks with Lewis Basic Pyridine Sites for Selective Detection of Ce 3+ Ions.

A highly symmetric bis-triazole-pyridine-based organic ligand, i.e., 3,5-di(4 H -1,2,4-triazol-4-yl)pyridine ( L ), and Cu(II) salts were used to synthesize three cationic Cu(I) metal-organic frameworks (MOFs), namely, {[Cu(L)]·(NO 3 )·(H 2 O)} n ( 1 ), {[Cu(L)]·(BF 4 )·0.5H 2 O} n ( 2 ), and {[Cu 1.25 (L)]·1.25(ClO 4 )·H 2 O} n ( 3 ). All three MOFs have nonbonded anions situated inside the pore spaces. Both 1 and 2 have a two-dimensional network structure, while 3 has a three-dimensional structure. All three MOFs were characterized using Fourier transform infrared spectroscopy, elemental (C, H, and N) analysis, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. Due to the presence of a Lewis basic pyridine moiety, these MOFs could serve as luminescent probes for the selective detection of Ce 3+ ions with excellent efficiency (10 -7 M). The synthesis of Cu(I)-based MOFs and their use to detect Ce 3+ ions in water via a turn-on fluorescence process have rarely been reported. These MOFs are highly stable in water, are recyclable, and function efficiently at different pH values.