Enhanced Luminescence of Dye-Decorated ZIF-8 Composite Films via Controllable D–A Interactions for White Light Emission
Qiufen Liu, Xuelei Chen, Jiahao Wu, Liming Zhang, Guanjie He, Shouqin Tian, Xiujian Zhao
Abstract
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 (H 3 BTC-ZIF-8) via introducing the 1,2,4-benzenetricarbonic acid (H 3 BTC) ligand into the ZIF-8 sol system. Moreover, H 3 BTC-ZIF-8 was used for the loading of organic fluorescent dyes rhodamine 6G (R6G) and coumarin 151 (C151) to prepare R6G/C151/H 3 BTC-ZIF-8 composite films. A white-light-emitting composite film (R6G/C151/H 3 BTC-ZIF-8) with CIE coordinates of (0.323, 0.347) was successfully prepared by compounding fluorescent dyes (R6G and C151) with H 3 BTC-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 H 3 BTC (48.0%) compounded with the same concentrations of dyes. The fluorescence enhancement was probably attributed to an increased amount of active sites of H 3 BTC-modified ZIF-8 interacting with dyes C151 and R6G. This can form hydrogen bonds between H 3 BTC-ZIF-8 and C151, and weak electron donor–acceptor (D–A) interactions between H 3 BTC-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.