Cadmium－Organic Frameworks Based on N-(Pyridin-4-yl)-4-(pyridin-4-yl)-1,8-naphthalimide and Aromatic Dicarboxylic Acids: Synthesis, Structures, CO2 Adsorption, and Detection of Nitro Compounds

[[abstract]]本研究透過硝酸鎘、雙?啶橋接配體N-(pyridin-4-yl)-4-(pydrin-4-yl)-1,8naphthalimide (NI-bipy-44)、芳香類二酸有機配體利用溶劑熱反應合成出一系列具螢光性的金屬-有機框架化合物 [Cd2(1,4-bdc)2(NI-bipy-44)2] (1, 1,4-H2bdc = 1,4-benzenedicarboxylic acid)、[Cd2(1,4-bdc-Br)2(NI-bipy-44)2] (2, 1,4-H2bdc-Br = 2-bromoterephthalic acid)、[Cd2(1,4-bdc-NO2)2(NI-bipy-44)2] (3, 1,4-H2bdc-NO2 = 2-nitroterephthalic acid)、[Cd2(BPDC)2(NI-bipy-44)2] (4, H2BPDC = biphenyl-4,4′-dicarboxylic acid)。化合物1-4具有相同的拓樸結構，均為三維的孔洞型層柱狀結構，孔洞佔有率分別為58.4 % (1)、51.4 % (2)、51.5 % (3)、41.4 % (4)，其中化合物4具有二次互穿的特性。 化合物1-4在450 ± 5 nm有高螢光訊號，可用於有機溶劑小分子和硝基化合物螢光感測。當化合物1和化合物2浸泡於H2O和DMSO後，會有明顯的螢光焠熄，化合物4浸泡o-xylene和p-xylene後則發生螢光增強。溶液相硝基感測實驗顯示化合物1-4對2-硝基苯酚，3-硝基苯酚，4-硝基苯酚和1,4-二硝基苯具有較佳的螢光焠熄表現，發現苯酚類化合物同時具有－NO2與－OH造成螢光焠熄的效果更為明顯。對於烷基類硝基化合物:硝基甲烷和2,3-二甲基-2,3-二硝基丁烷，較無明顯的螢光焠熄現象，具有選擇性感測的潛力。氣相硝基感測實驗可看出化合物1和化合物2對硝基苯，2-硝基苯酚，4-硝基 甲苯有明顯的感測效果，化合物4則對硝基苯和2-硝基苯酚有較佳的感測表現，主要原因為蒸氣壓所造成的濃度差異。另外，對氣相碘分子進行吸附研究。結果顯示化合物1-4吸附碘分子後可造成螢光焠熄達到90 %以上，且晶體顏色明顯的轉變為咖啡色。特別是化合物2在吸附10分鐘後螢光焠熄即高達90 %，具有快速偵測碘分子能力。我們也研究了這些金屬-有機框架化合物對二氧化碳的吸附能力，結果顯示雖然化合物1-4都具有高孔洞性，但效果都不佳。[[abstract]]A series of fluorescent metal－organic frameworks (MOFs) based on Cd(II) and N-(pyridin-4-yl)-4-(pydrin-4-yl)-1,8-naphthalimide (NI-bipy-44) with different aromatic dicarboxylates were synthesized. [Cd2(1,4-bdc)2(NI-bipy-44)2] (1, 1,4-H2bdc = 1,4-benzenedicarboxylic acid), [Cd2(1,4-bdc-Br)2(NI-bipy-44)2] (2, 1,4-H2bdc-Br = 2-bromoterephthalic acid), [Cd2(1,4-bdc-NO2)2(NI-bipy-44)2] (3, 1,4-H2bdc-NO2 = 2-nitroterephthalic acid), and [Cd2(BPDC)2(NI-bipy-44)2] (4, H2BPDC = biphenyl-4,4′-dicarboxylic acid) have similar structures suiting a 3D pillared-layer framework with porosity of 58.4%, 51.4%, 51.5%, and 41.4%, respectively. Of note, compound 4 is 2-fold interpenetration, while compounds 1-3 are non-interpenetration. Compounds 1-4 exhibit intense solid-state photoluminescence with λmax of 450 ± 5 nm, making them useful for detecting small organic molecules and nitro compounds.When compounds 1 and 2 were soaked in H2O and DMSO, there was a significant fluorescence quenching. On the other hand, compounds 4 soaked with o-xylene and p-xylene would result in fluorescence enhancement.After immersing compounds 1-4 in DMF solutions of nitro compounds, their luminescence could be efficiently and selectively quenched by a series of nitroaromatics, especially 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), and 1,4-dinitrobenzene (1,4-DNB), but not by aliphatic nitro analytes, such as nitromethane (NM) and 2,3-dimethyl-2,3-dinitrobutane (DMNB). On the other hand, when the photoluminescence sensing studies of the nitro analytes were carried out in the vapor phase, it was observed that nitrobenzene (NB), 2-NP, and 4-NP are effective quenchers. The quenching efficiency is approximately consistence with the vapor pressure of analytes. Studies on adsorption of iodine vapor showed that compounds 1-4 can adsorb iodine molecules, resulting in more than 90% fluorescence quenching and significant crystal color-changing from colorless to brown. In particular, compound 2 exhibits the ability to rapidly detect iodine molecules with fluorescence quenching up to 90% after 10 minutes of adsorption.Finally, compounds 1-4 display very poor carbon dioxide uptake ability even though they are high porosity.[[note]]碩