AIE‐Driven Chiral Covalent Organic Frameworks for Solid‐State Circularly Polarized Luminescence, Hydrochromism, and Water‐Induced Chiroptical Enhancement
Mengjuan Zuo, Xinlin Zha, Zhenzhen Jiang, Mengying Luo, Zhong Yan, Haining You, Xing Qing, Yi Xiong, Ying Liu, Liu Liu, Yingying Li, Wen Wang, Mufang Li, Dong Wang
Abstract
Abstract Chiral covalent organic frameworks (CCOFs) are promising candidates for chiral optoelectronics and sensing, but their weak solid‐state fluorescence and chiroptical responses often limit practical utility. Here, we introduce a novel CCOF synthesized from achiral monomers, 2‐hydroxy‐1,3,5‐benzenetricarbaldehyde and hydrazine, via imine condensation with a chiral induction strategy, yielding salicylaldehyde azine units with aggregation‐induced emission. Optimized catalyst and chiral inducer stoichiometry endow the framework with exceptional chiroptical properties (|g abs | = 2.2 × 10 −2 , ellipticity ≈ 1000 mdeg). In the solid state, the CCOF exhibits intense red fluorescence (λ em ≈ 645 nm) with a large stoke shift and favorable circularly polarized luminescence (CPL, |g lum | = 5.2 × 10 −2 ), marking the first CCOF derived solely from achiral building blocks with robust solid‐state CPL. When integrated into polydimethylsiloxane, it forms flexible and semitransparent composite films suitable for CPL‐based applications. The CCOF also functions as a highly enantioselective fluorescent sensor for chiral analytes, including 2‐aminocyclohenanol and dimethyl‐1,2‐cyclohexanediamine. Furthermore, it demonstrates reversible hydrochromism, transitioning from yellow to orange (ΔE ≈ 42.7), and water‐induced chiroptical enhancement (ellipticity up to 2100 medg, |g abs | = 5.5 × 10 −2 ), achieving the highest ground‐state chirality reported for CCOFs through enol‐to‐keto tautomerism upon water adsorption. This stimuli‐responsive CCOF overcomes persistent limitations in solid‐state CPL and paves the way for chiral sensing, optical displays, and responsive materials.