Blue-Emitting Ligand-Mediated Assembly of Rare-Earth MOFs toward White-Light Emission, Sensing, Magnetic, and Catalytic Studies.

New lanthanide carboxylate compounds with two- (2D) and three-dimensional (3D) structures have been prepared by employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) as an organic linker. The compounds, [Ln(C 14 H 8 O 6 )(C 7 O 3 H 4 )·2H 2 O]·4(H 2 O), Ln = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy and [Ln(C 7 O 3 H 4 ) 3 ·(C 3 H 7 ON)·(H 2 O)]·2(H 2 O)(C 3 H 7 NO), Ln = La, Ce, Pr, have two- and three-dimensional structures, respectively. In all compounds, lanthanide ions are connected together, forming a dimer, which is connected by the 2,5-BPTA ligand. In the two-dimensional structure, there are two 2,5-BPTA moieties present, and in the three-dimensional structure, there are three 2,5-BPTA moieties present. The lanthanide centers are nine-coordinated, the 2D structure has a tricapped trigonal prismatic arrangement, and the 3D structure has a monocapped distorted square antiprismatic arrangement. The Pr compound forms in both 2D and 3D structures, whose formation depends on the time of the reaction (2 days─2D and 5-6 days─3D). The ligand emits in the blue region, and using the characteristic emission of Eu 3+ (red) and Tb 3+ (green) ions, we achieve white light emission in the (Y 0.96 Tb 0.02 Eu 0.02 ) compound. The overall quantum yield for the white light emission is 28%. The strong green luminescence of the Tb 3+ -containing compound was employed to selectively sense the Cr 3+ and Fe 3+ ions in aqueous solution with limits of detection (LODs) at 0.41 and 8.6 ppm, respectively. The Tb compound was found to be a good heterogeneous catalyst for the Ullman-type O-arylation reaction between phenol and bromoarene with yields of 95%. Magnetic studies on the Gd-, Tb-, and Dy-containing compounds showed weak exchange interactions within the dimeric Ln 2 units. The present work demonstrates the many utilities of the rare-earth-containing MOFs, especially toward white-light emission, metal-ion sensing, and heterogeneous catalysis.