Gui Bo, Meng Yi, Xie Yang, Tian Jianwu, Yu Ge, Zeng Weixuan, Zhang Guanxin, Gong Shaolong, Yang Chuluo, Zhang Deqing, Wang Cheng
Key Laboratory of Biomedical Polymers of Ministry of Education, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, China.
Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
Adv Mater. 2018 Jul 4:e1802329. doi: 10.1002/adma.201802329.
The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water-stable anthracene and maleimide appended zirconium-based-metal-organic framework (Zr-MOF; UiO-68-An/Ma) is reported. Unlike the regular intramolecular "fluorophore-spacer-receptor" format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo-intramolecular fluorescent PET process, resulting in UiO-68-An/Ma with very weak fluorescence. Interestingly, after Diels-Alder reaction or thiol-ene reaction of maleimide groups, the pseudo-intramolecular fluorescent PET process in UiO-68-An/Ma fails and the solid-state fluorescence of the crystals is recovered. In addition, UiO-68-An/Ma shows an interesting application as solid-state fluorescent turn-on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET-based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli-responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.
将荧光光致电子转移（PET）开关/传感器固定到固态中一直是一个巨大的挑战，因为它们在固态中通常无法保持其在溶液中的相同性质。在此，报道了一种水稳定的、带有蒽和马来酰亚胺的锆基金属有机框架（Zr-MOF；UiO-68-An/Ma）。与常规的分子内“荧光团-间隔基-受体”形式不同，将荧光（蒽）和受体（马来酰亚胺）基团分别固定到多变量MOF的框架中也有利于伪分子内荧光PET过程，导致UiO-68-An/Ma的荧光非常微弱。有趣的是，在马来酰亚胺基团发生狄尔斯-阿尔德反应或硫醇-烯反应后，UiO-68-An/Ma中的伪分子内荧光PET过程失效，晶体的固态荧光得以恢复。此外，UiO-68-An/Ma作为生物硫醇的固态荧光开启传感器表现出有趣的应用，在5分钟内对低至50 μmol L的浓度有肉眼可见的响应。这项研究代表了一种在固态中有效调节荧光PET开关/传感器的通用策略，并且考虑到添加分析物/目标物种后基于PET的MOF的荧光可以恢复，这项研究肯定会激发未来构建用于有趣应用（例如逻辑门）的刺激响应荧光MOF。
