Liu Qiufen, Chen Xuelei, Wu Jiahao, Zhang Liming, He Guanjie, Tian Shouqin, Zhao Xiujian
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology (WUT), No. 122, Luoshi Road, Wuhan 430070, P. R. China.
School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
Langmuir. 2023 Mar 14;39(10):3656-3667. doi: 10.1021/acs.langmuir.2c03299. Epub 2023 Mar 1.
Metal-organic frameworks (MOFs) constructed by metal ions/clusters and organic linkers are used to encapsulate fluorescent guest species with aggregation-caused quenching (ACQ) effects to enhance fluorescence properties due to their porous structures and high specific surface areas. However, there would be a problem of matching between MOF pores and guest molecules' sizes. In this paper, amorphous ZIF-8 was modified by carboxyl functional groups (HBTC-ZIF-8) via introducing the 1,2,4-benzenetricarbonic acid (HBTC) ligand into the ZIF-8 sol system. Moreover, HBTC-ZIF-8 was used for the loading of organic fluorescent dyes rhodamine 6G (R6G) and coumarin 151 (C151) to prepare R6G/C151/HBTC-ZIF-8 composite films. A white-light-emitting composite film (R6G/C151/HBTC-ZIF-8) with CIE coordinates of (0.323, 0.347) was successfully prepared by compounding fluorescent dyes (R6G and C151) with HBTC-modified ZIF-8, whose photoluminescence quantum yield (PLQY) can reach 64.0%. It was higher than the PLQY of the composite films prepared by crystalline ZIF-8 (40.2%) or amorphous ZIF-8 without HBTC (48.0%) compounded with the same concentrations of dyes. The fluorescence enhancement was probably attributed to an increased amount of active sites of HBTC-modified ZIF-8 interacting with dyes C151 and R6G. This can form hydrogen bonds between HBTC-ZIF-8 and C151, and weak electron donor-acceptor (D-A) interactions between HBTC-ZIF-8 and R6G molecules, respectively, thus enhancing the interactions between dyes and ZIF-8 and reducing the ACQ effect existing between dye molecules. Therefore, this strategy could provide an important guidance to develop white-light-emissive materials.
由金属离子/簇和有机连接体构建的金属有机框架（MOF）由于其多孔结构和高比表面积，被用于封装具有聚集诱导猝灭（ACQ）效应的荧光客体物种，以增强荧光性能。然而，MOF孔与客体分子大小之间存在匹配问题。在本文中，通过将1,2,4-苯三甲酸（HBTC）配体引入ZIF-8溶胶体系，用羧基官能团对非晶态ZIF-8进行改性（HBTC-ZIF-8）。此外，HBTC-ZIF-8用于负载有机荧光染料罗丹明6G（R6G）和香豆素151（C151），以制备R6G/C151/HBTC-ZIF-8复合薄膜。通过将荧光染料（R6G和C151）与HBTC改性的ZIF-8复合，成功制备了CIE坐标为（0.323, 0.347）的白光发射复合薄膜（R6G/C151/HBTC-ZIF-8），其光致发光量子产率（PLQY）可达64.0%。它高于由结晶ZIF-8（40.2%）或不含HBTC的非晶态ZIF-8（48.0%）与相同浓度染料复合制备的复合薄膜的PLQY。荧光增强可能归因于HBTC改性的ZIF-8与染料C151和R6G相互作用的活性位点数量增加。这分别可以在HBTC-ZIF-8和C151之间形成氢键，以及在HBTC-ZIF-8和R6G分子之间形成弱电子供体-受体（D-A）相互作用，从而增强染料与ZIF-8之间的相互作用，并减少染料分子之间存在的ACQ效应。因此，该策略可为开发白光发射材料提供重要指导。
