Design of a dual-functional In(III)-MOF based on a triazine skeleton: Selective C2H2 capture and fluorescent sensing of TNP in aqueous media

Metal-organic frameworks (MOFs) have emerged as a multi-functional platform for selective gas capture and luminescent detection of harmful pollutants, in which their pore functionality and structural stability are two key factors to be considered for the targeted applications. In this contribution, we present the synthesis and structural evaluation of a new channel-type MOF formulated as {[In3(OH)3(TATAB)2](DMA)8(CH3CN)6(H2O)2}n (1, DMA is short for N,N-dimethylacetamide and TATAB is the abbreviation of 4,4′,4″-s-triazine-1,3,5-triyl-p-aminobenzoate) constructed from rod-like [In-(OH)-(COO)2]n chains and the N-rich fluorescent triazine ligand H3TATAB. The noninterpenetrated framework of 1 features 1D rhombic channels (13.1 × 14.2 Å2) along the c axis with abundant of free N sites on the pore walls. The solvent-removal framework of 1 (1a) could adsorb large amount of C2H2 (154 cm3/g) at 298 K and 1 bar with a moderate C2H2/CO2 selectivity (3.7), and its separation performance has been further validated via the break-through experiments. Aqueous-phase sensing experiments demonstrate this MOF exhibits excellent performance of fluorescent detection of 2,4,6-trinitrophenol (TNP) via remarkable fluorescence quenching and obvious blue-shift of maximum emission. In connection to the sensing experiments, we used DFT calculations to reveal the underlying mechanism of such sensing performances via analyzing the energy lever together with electron transfer route.