以咔唑雙吡啶與直線型芳香二酸製備鋅金屬有機框架化合物：合成、結構鑑定、氣體吸附與硝基化合物及離子感測

本研究透過鈴木偶聯反應合成出二個有機配體咔唑雙吡啶，分別為3,6-bis(pyridin-4-yl)-9H-carbazole 與9-n-propyl-3,6-bis(pyridin-4-yl)-9H-carbazole(bphc 與bppc)，並以之與硝酸鋅及三種直線型芳香二酸經溶劑熱合成法製備出五個金屬有機框架化合物，分別為[Zn2(OH)(NO2-1,4-bdc)1.5(bphc)] (1，NO2-1,4-H2bdc = 2-nitrobenzene-1,4-dicarboxylic acid) 、[Zn2(OH)(NO2-1,4-bdc)1.5(bppc)] (2) 、[Zn2(OH)(Br-1,4-bdc)1.5(bphc)] (3，Br-1,4-H2bdc = 2-bromobenzene-1,4-dicarboxylic acid)、[Zn2(OH)(Br-1,4-bdc)1.5(bppc)] (4)、[Zn2(OH)(1,4-ndc)1.5(bphc)] (5，1,4-H2ndc = 1,4-naphthalenedicarboxylic acid)。化合物 1—5 皆為二維層狀結構，鋅金屬形成Zn4(OH)2(O2C)6 的二級建構元團簇，透過芳香二酸以及咔唑雙吡啶配位連接形成二維平面框架，平面之間以互相平行的方式堆疊並形成微孔通道，孔隙率分別為6.3%、1.9%、6.4%、3.4%和6.1%。化合物 1—5 對 CO2 和 N2 的吸附表現不佳，在195 K 和 P/P0 = 1 時對CO2 的吸附值依序為36.1、6.1、11.1、4.8 和3.3 cm3/g，在77 K 以及 P/P0 = 1 時對N2 的吸附值分別為5.0、3.0、11.2、17.2 和3.3 cm3/g。由上述可知，當對苯二甲酸的2-位取代基為硝基時，具有較好的CO2 吸附能力，推測是金屬有機框架與氣體分子之間的靜電作用力影響CO2 之吸附值；其次，當有機配體為bphc時有較好的CO2 之吸附能力，推測為咔唑雙吡啶的取代基團之空間位阻效應影響CO2 吸附值。化合物 1—5 具高螢光性可用於感測硝基化合物。化合物 1—5 之二甲基乙醯胺懸浮液加入的4-硝基苯酚時皆有明顯的螢光焠熄，但加入烷基類硝基化合物如硝基甲烷和2,3-二甲基-2,3-二硝基丁烷則無明顯的效果。此焠熄現象可歸結於電子轉移機制。化合物 1—5 之水相懸浮液可感測離子，正三價陽離子如Fe3+、Al3+ 和 Cr3+除了有螢光會發生紅移的現象，隨芳香二酸的不同，會伴隨螢光增強或是焠熄；另外，加入CrO42-、Cr2O72- 和 MnO4- 等陰離子則會有明顯的螢光焠熄。干擾離子實驗以及偵測極限量測證實化合物1—5 有良好的選擇性離子感測表現以及低偵測濃度，顯示化合物1—5 可做為良好的離子螢光感測材料。

關鍵字

螢光感測；硝基化合物；陽離子；陰離子

並列摘要

Two new organic ligands 3,6-bis(pyridin-4-yl)-9H-carbazole (bphc) and 9-n-propyl-3,6-bis(pyridin-4-yl)-9H-carbazole (bppc) have been synthesized by Suzuki-coupling. Hydrothermal reactions of bphc or bppc with Zn(NO3)2‧6H2O and linear aromatic dicarboxylic acids yielded five new metal−organic frameworks (MOFs), namely [Zn2(OH)(NO2-1,4-bdc)1.5(bphc)] (1, NO2-1,4-H2bdc = 2-nitrobenzene-1,4-dicarboxylic acid), [Zn2(OH)(NO2-1,4-bdc)1.5(bppc)] (2), [Zn2(OH)(Br-1,4-bdc)1.5(bphc)] (3, Br-1,4-H2bdc = 2-bromobenzene-1,4-dicarboxylic acid), [Zn2(OH)(Br-1,4-bdc)1.5(bppc)] (4) and [Zn2(OH)(1,4-ndc)1.5(bphc)] (5, 1,4-H2ndc = 1,4-naphthalenedicarboxylic acid). Compounds 1—5 have similar 2D layer structure, constructed from {Zn4(OH)2(O2C)6} clusters connecting by dicarboylates and carbazole containing bispyridyl ligands. These 2D layers are stacked parallel to form microporous channels with porosities of 6.3, 1.9, 6.4, 3.4, and 6.1% for compounds 1—5 , respectively. Compounds 1—5 have shown very poor gas adsorption abilities, with CO2 uptakes of 36.1, 6.1, 11.1, 4.8, and 3.3 cm3/g, respectively, at 195 K and P/P0 = 1, and N2 uptakes of 5.0, 3.0, 11.2, 17.2, and 3.3 cm3/g, respectively, at 77 K and P/P0 = 1. Compounds 1—5 exhibit strong fluorescene and thus can be used as sensing materials. The fluorescence of compounds 1 — 5 dispersed in DMAc would be obviously quenched when 4-nitrophenol was added (quenching efficiency > 99%). Nitro aliphatic compounds such as nitromethane and 2,3-dimethyl-2,3-dinitrobutane did not show significant quenching effect. Such fluorescence quenching phenomena might be attributed to the electron transfer mechanism. The aqueous suspensions of compounds 1—5 could be utilized in sensing trivalent cation such as Fe3+, Al3+, and Cr3+ ions, with significant redshift in wavelength associated with fluorescene enhancement or quenching depending on the dicarboxylates. Further, addition of CrO42-, Cr2O72-, and MnO4- would effectively quench the fluorescence of compounds 1—5 dispersed in water (quenching efficiency > 64%). Notably, the aqueous suspensions of compounds 1—5 display remarkable selective and sensitive sensing for both cation and anion, as a result of the interference and limit of detection (LOD) studies.