Heterometallic 3-D Zn/Ca Metal–Organic Frameworks Based on V-Shaped Angular Tetracarboxylic Ligands as Selective Fluorescence Sensors for Nitroaromatic Explosive Vapors

High Resolution Image Download MS PowerPoint Slide A family of heterometallic Zn/Ca MOFs based on angular tetracarboxylic ligands with formulas [ZnCa(L)(S)(S′)] n (S, S′ = H 2 O or S = H 2 O, S′ = DMF) UCY-18 (L) (H 4 L = 4,4′-hexafluoroisopropilidene diphthalic acid (H 4 HFPD), 3,3′,4,4′-benzophenone tetracarboxylic acid (H 4 BPTC), 4,4′-oxydiphthalic acid (H 4 ODPA), 4,4′-azanediyl diphthalic acid (H 4 ADPA)) is reported. The crystal structures of UCY-18 (L) comprise 3-D networks based on helical one-dimensional chain SBUs [ZnCa(L 4– )] containing tetragonal channels along the crystallographic a -axis. Gas sorption studies on activated UCY-18 (L) indicated appreciable BET surface areas ranging from 1338 to 2134 m 2 g –1 . Selected vapor sorption studies indicated the affinity of these materials toward representative C 6 -aromatic and nonaromatic organic molecules. Thin films of UCY-18 (HFPD), UCY-18 (ODPA), and UCY-18 (ADPA) embedded in poly(vinylidene fluoride) were fabricated and evaluated for their sensing capability for vapors of selected nitroaromatic compounds. The thin films exhibit high selectivity in detecting 2,4,6-trinitrophenol and 2,4,6-trinitrotoluene vapors among other nitroaromatic compounds and interferents at equal concentration. The crystal structures of UCY-18 (HFPD) loaded with nitrobenzene and 2-nitrotoluene provided useful information about the interactions of the MOFs with these nitroaromatic molecules. Overall, this work highlights the potential of heterometallic Zn/Ca MOF chemistry to afford microporous MOFs containing highly accessible metal centers and displaying the capability to recognize vapors of selected analytes.