A New Eu(III)-Based Metal-Organic Framework: Synthesis, Characterization, Fluorescence Detection of Nitrobenzene and Catalytic Conversion of CO2

The employment of metal-organic frameworks (MOFs) as fluorescence sensors for the detection of environmental pollutants and/or heterogeneous catalysts for CO2 conversion is of great importance for protecting human health. For this purpose, we synthesized a new Eu-MOF [Eu2(btpdc)2·(HCOO)2]n (1) (H2btpdc = benzo[b]thiophene-2,5-dicarboxylic acid) with its three-dimensional structure characterized by single-crystal X-ray diffraction. The powder X-ray diffraction (PXRD) and thermal gravimetric analysis (TGA) results indicate that 1 has high chemical durability, good water stability and high thermal stability. Fluorescence sensing investigations demonstrate that 1 is a smart chemical sensor towards nitrobenzene (NB) detection with high sensitivity, high selectivity and good regeneration performance. A high quenching constant (Ksv = 2.33 × 105 M−1) and a low detection limit (LOD = 0.038 μM) are obtained. Combined with experiments and density functional theory calculations, the mechanism of fluorescence quenching of 1 by NB was also revealed. Furthermore, 1 can serve as a smart catalyst for the cycloaddition reaction of CO2 with epoxides to synthesize cyclic carbonates, displaying high activity, high selectivity, and good generality.