Triazole-Based Cu(I) Cationic Metal–Organic Frameworks with Lewis Basic Pyridine Sites for Selective Detection of Ce<sup>3+</sup> Ions
Sandeep Kumar, Shixuan Ma, Brij Mohan, Shuangshuang Li, Peng Ren
Abstract
A highly symmetric bis-triazole-pyridine-based organic ligand, i.e., 3,5-di(4H-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)]·(NO3)·(H2O)}n (1), {[Cu(L)]·(BF4)·0.5H2O}n (2), and {[Cu1.25(L)]·1.25(ClO4)·H2O}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 Ce3+ ions with excellent efficiency (10–7 M). The synthesis of Cu(I)-based MOFs and their use to detect Ce3+ 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.