Fluorescent Cadmium Bipillared-Layer Open Frameworks: Synthesis,Structures, Sensing of Nitro Compounds,and Capture of Volatile Iodine |
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Authors: | Tang-Ching Chen Dr Meng-Jung Tsai Prof?Dr Jing-Yun Wu |
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Institution: | Department of Applied Chemistry, National Chi Nan University, Nantou, 545 Taiwan |
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Abstract: | Fluorescent Cd metal–organic frameworks (MOFs), Cd2(dicarboxylate)2(NI-bpy-44)2] (dicarboxylate=benzene-1,4-dicarboxylate (1,4-bdc, 1 ), 2-bromobenzene-1,4-dicarboxylate (Br-1,4-bdc, 2 ), 2-nitrobenzene-1,4-dicarboxylate (NO2-1,4-bdc, 3 ), biphenyl-4,4′-dicarboxylate (bpdc, 4 ); NI-bpy-44=N-(pyridin-4-yl)-4-(pyridin-4-yl)-1,8-naphthalimide)), featuring non- and twofold interpenetrating pcu -type bipillared-layer open structures with sufficient free voids of 58.4, 51.4, 51.5, and 41.4 %, respectively, have been hydro(solvo)thermally synthesized. MOFs 1 – 4 emitted solid-state blue or cyan fluorescence emissions at 447±7 nm, which mainly arose from NI-bpy-44 and are dependent on the incorporated solvents. After immersing the crystalline samples in different solvents, that is, H2O and DMSO ( 1 and 2 ) as well as nitrobenzene and phenol ( 1 – 4 ), they exhibited a remarkable fluorescence quenching effect, whereas o-xylene and p-xylene ( 4 ) caused significant fluorescence enhancement. The sensing ability of MOFs 1 – 4 toward nitro compounds carried out in the vapor phase showed that nitrobenzene and 2-nitrophenol displayed detectable fluorescence quenching with 1 , 2 , and 4 whereas 4-nitrotoluene was an effective fluorescence quencher for 1 and 2 ; this is most likely attributed to their electron-deficient properties and higher vapor pressures. Moreover, MOFs 1 – 4 are highly reusable for quick capture of volatile iodine, as supported by clear crystal color change and also by immense fluorescence quenching responses owing to the donor–acceptor interaction. Low-pressure CO2 adsorption isotherms indicate that activated materials 1′ – 4′ are inefficient at taking up CO2. |
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Keywords: | cadmium fluorescence iodine metal–organic frameworks nitro compounds |
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