Fluolab【JACS】东南大学陈旭漫|g因子动态变化达0.035！光控手性共价有机框架实现时间演变圆偏振发光
文章标题： Time-Evolving Reversible Circularly Polarized Luminescence Enabled by Light-Fueled Dissipative Self-Assembly of Covalent Organic Frameworks
通讯作者： Xu-Man Chen
文章概要
引言
在智能材料领域，光控发光材料因其非侵入性、响应迅速及清洁等特点，在显示技术、信息加密及生物成像等前沿领域展现出巨大潜力。其中，圆偏振发光（CPL） 作为一种独特的发光形式，在量子信息载体和三维显示中具有不可替代的作用。然而，开发同时具备高不对称因子（） 和宽调节范围的智能CPL材料仍面临巨大挑战。传统的分子开关在光异构化过程中往往会破坏预组织的手性排列，导致手性活性降低。本研究创新性地提出利用共价有机框架（COFs） 的有序多孔结构作为手性支架，通过光燃料驱动的耗散自组装（DSA） 策略，成功构建了一种具有时间演变特性且可逆调节的高性能CPL平台，为设计多维信息加密材料提供了新思路。
Scheme 1. (a) Synthesis of β-Cyclodextrin-Functionalized Covalent Organic Frameworks (CyDCOF) and the CyDCOF/Fluorophore System, a Multicolor CPL Platform. (b) The CyDCOF/Fluorophore/MEH and CyDCOF/Fluorophore/SP System, a Time-Evolving Reversible Photocontrolled CPL Platform, and the Display of Its Mixed-Matrix Film. (c) The Illustration and Molecular Structures of MEH, SP, N3-β-CyD, and Fluorophores
主要实验及结论
研究人员首先通过点击化学将叠氮化修饰的β-环糊精接枝到炔基修饰的COF骨架上，合成了手性框架材料CyDCOF。实验表征显示，该材料保留了良好的结晶度和高度有序的蜂窝状孔道结构。利用CyDCOF作为手性宿主平台，研究团队将其与多种阿基拉（Achiral）荧光团结合。在手性空间限域效应、静电作用和π-π堆积的共同驱动下，成功将手性传递至荧光分子，实现了涵盖蓝、绿、黄、橙、红的全色域CPL发射。值得注意的是，这种基于COF的限域效应显著放大了手性信号，使系统在基态表现出极弱的手性，但在激发态下展现出高达量级的不对称因子。
Figure 1. (a) Structural schematic diagrams and pictures of the alkynyl COF and CyDCOF. (b) FT-IR spectra of the alkynyl COF and CyDCOF. (c) SAXS patterns of the alkynyl COF and CyDCOF. (d) Solid-state 13C CP/MAS NMR of CyDCOF. (e) N2 adsorption–desorption isotherms for the alkynyl COF and CyDCOF. (f) TG curves of the alkynyl COF and CyDCOF. (g) SEM and (h–j) TEM images of CyDCOF. (i) A higher-magnification image of the area outlined in image (h), and (j) a higher-magnification image of the area outlined in image (i).
Figure 2. (a) Chemical structures of five fluorophores and the pictures of CyDCOF/fluorophore systems. (b) Normalized UV–vis spectra, (c) normalized FL spectra, (d) CIE chromaticity diagram, and (e) CPL signal ΔI (IntensityLeft – IntensityRight) of CyDCOF/fluorophore systems. The full width at half-maximum of the CPL and the comparison of ΔI between β-CyD/fluorophore, alkynyl COF/fluorophore, amorphous CyD-polymer/fluorophore, and CyDCOF/fluorophore systems for (f) D4, (g) AO, (h) ESY, (i) Rh B, and (j) NR.
Figure 3. Characterization of DSA systems. (a) Optical transmittance at 700 nm of the various constituents. The corresponding cubic error bars. n = 5 independent experiments, with the bar data indicating mean ± SD. (b) Fluorescence microscopy image of the CyDCOF/D4/MEH, and (c) the other image acquired under 350 nm excitation. (f) Zeta potential and dynamic light scattering of (d) CyDCOF, (g) CyDCOF/MEH and CyDCOF/SP, and (j) CyDCOF/D4/MEH and CyDCOF/D4/SP. TEM images of (e) CyDCOF (nanosized), (h) CyDCOF/MEH, (i) CyDCOF/SP, (k) CyDCOF/D4/MEH, and (l) CyDCOF/D4/SP.
为了引入动态调节功能，团队在系统中加入了光致变色开关磺酸基梅罗蓝（MEH）。在420 nm光照诱导下，MEH发生环化反应转变为螺吡喃（SP）态，这一过程触发了系统内部的耗散自组装行为，导致荧光强度和CPL信号发生显著改变。以D4荧光系统为例，光照使系统从平衡态演变为非平衡的瞬态组装体，其CPL信号随时间动态演化，并在停止光照后通过热弛豫逐渐恢复初态。此外，研究人员进一步将该系统整合到聚乙二醇（PEG）基质中制备成混合基质薄膜。该薄膜表现出卓越的光学性能，其值在光照和热处理过程中可在-0.009至-0.044之间切换。高达0.035的动态调节范围是目前已知COF类CPL材料中的领先水平。利用这一特性，团队成功实现了具有自抹除功能的光学图案编写，在防伪和信息存储领域展示了极高的实用价值。
Figure 4. Normalized FL, ΔI, and fluorescence kinetics variation from the SP state to MEH state, of the CyDCOF/fluorophore/MEH system: (a–c) for D4, (d–f) for ESY, and (g–i) for AO. (j) Normalized FL and ΔI of the CyDCOF/NR/MEH system. (k) CIE chromaticity diagram and (l) pictures of CyDCOF/fluorophore/MEH and CyDCOF/fluorophore/SP. (m) The average ΔI at 423 nm. Points: mean ± SD (n = 5 independent experiments). Solid curve: B-spline fitting. Red shaded area: 95% CI. (n) The average Δ_I_ at 423 nm of five cycles. The corresponding cubic error bars. n = 3 independent experiments, with the bar data indicating mean ± SD.
Figure 5. (a) Normalized FL intensity, ΔI, and glum value and (b) CD spectra of PEG1, PEG1MEH, and PEG1SP. (c) UV–vis absorbance variation and (d) Δ_I_ variation from PEG2SP to PEG2MEH. (e) The combination of PEG1film and left circular polarizer into a device. (f) The periodic variation of FL intensity at 430 nm upon rotation, θ (0°–360°). (g) Absorbance at 425 nm increasing kinetics right after 5 s of 420 nm irradiation and kept in the dark at 25 °C from PEG2SP to PEG2MEH. (h) The illustration and images for the photowriting and self-erasing process of the film. (i) FL intensity at 425 nm–time profile and corresponding fluorescence images of the film over five cycles of photochromic switching (coloration and fading).
总结及展望
本研究通过一种简便且可扩展的策略，成功构建了基于环糊精修饰手性COF的动态CPL平台。该工作不仅实现了高纯度的多色圆偏振光输出，更利用耗散自组装原理赋予了材料光控的时间相关动态响应特性。制备的混合基质薄膜凭借其优异的加工性、可逆性以及高达39%的绝对量子产率，在多级信息防伪、光子逻辑器件及动态3D显示等领域表现出广阔的应用前景。未来，研究团队将致力于优化材料的弛豫动力学过程，并进一步探索其在生物成像等复杂环境中的表现，推动智能手性发光材料向集成化和实用化迈进。