Microporous Hydrogen-Bonded Organic Framework for Highly Efficient Turn-Up Fluorescent Sensing of Aniline

A microporous three-dimensional (3D) hydrogen-bonded organic framework (HOF-20) has been constructed from an aromatic-rich tetratopic carboxylic acid, 5-(2,6-bis­(4-carboxyphenyl)­pyridin-4-yl)­isophthalic acid (H4BCPIA). The activated HOF-20a has a moderately high Brunauer–Emmett–Teller (BET) surface area of 1323 m2 g–1 and excellent stability in water and HCl aqueous solution. HOF-20 exhibits highly efficient turn-up fluorescent sensing of aniline in water with a detection limit of 2.24 μM and is selective toward aniline in the presence of aromatic interferents, owing to the hydrogen bonding and edge-to-face π–π stacking interactions between the HOF-20 host and the guest aniline molecules, as demonstrated in the single-crystal X-ray structure of HOF-20⊃aniline. Density functional theory (DFT) calculations further demonstrate that the recognition of aniline molecules by HOF-20 could restrict the rotation of the aromatic rings in H4BCPIA linkers, reducing the nonradiative decay pathways upon photoexcitation and subsequently enhancing the fluorescence intensity.本研究以富芳族四元羧酸5-(2,6-双(4-羧基苯基)吡啶-4-基)间苯二甲酸（H4BCPIA）为构筑基元，成功构建了微孔三维氢键有机框架（hydrogen-bonded organic framework, HOF-20）。活化后的HOF-20a具备1323 m²·g⁻¹的中等偏高的布鲁诺尔-埃米特-特勒（Brunauer–Emmett–Teller, BET）比表面积，且在水与盐酸水溶液中展现出优异的稳定性。HOF-20对水溶液中的苯胺展现出高效的开启型荧光传感性能，检测限达2.24 μM；在芳香族干扰物共存的条件下，该材料仍对苯胺具有优异的选择性，这一现象源于HOF-20主体与客体苯胺分子间的氢键作用及边对面π-π堆积相互作用，该结论通过HOF-20⊃苯胺的单晶X射线结构得以验证。密度泛函理论（density functional theory, DFT）计算进一步证实，HOF-20对苯胺分子的识别可限制H4BCPIA配体中芳香环的旋转，减少光激发过程中的非辐射衰变路径，进而增强荧光发射强度。