Department of Chemistry and Biochemistry , University of South Carolina , Columbia , South Carolina 29208 , United States.
Department of Mathematics , University of South Carolina , Columbia , South Carolina 29208 , United States.
J Am Chem Soc. 2018 Jun 20;140(24):7611-7622. doi: 10.1021/jacs.8b02994. Epub 2018 Jun 12.
Stimuli-responsive materials are vital for addressing emerging demands in the advanced technology sector as well as current industrial challenges. Here, we report for the first time that coordinative integration of photoresponsive building blocks possessing photochromic spiropyran and diarylethene moieties within a rigid scaffold of metal-organic frameworks (MOFs) could control photophysics, in particular, cycloreversion kinetics, with a level of control that is not accessible in the solid state or solution. On the series of photoactive materials, we demonstrated for the first time that photoisomerization rates of photochromic compounds could be tuned within almost 2 orders of magnitude. Moreover, cycloreversion rates of photoresponsive derivatives could be modulated as a function of the framework structure. Furthermore, through MOF engineering we were able to achieve complete isomerization for coordinatively immobilized spiropyran derivatives, typically exhibiting limited photoswitching behavior in the solid state. For instance, spectroscopic analysis revealed that the novel monosubstituted spiropyran derivative grafted to the backbone of the MOF pillar exhibits a remarkable photoisomerization rate of 0.16 s, typical for cycloreversion in solution. We also applied the acquired fundamental principles toward mapping of changes in material properties, which could provide a pathway for monitoring material aging or structural deterioration.
刺激响应材料对于满足先进技术领域以及当前工业挑战的新兴需求至关重要。在这里，我们首次报道了将光响应结构单元配位集成到金属-有机骨架（MOF）的刚性骨架中，这些结构单元具有光致变色螺吡喃和二芳基乙烯部分，可以控制光物理性质，特别是环化动力学，其控制程度在固态或溶液中是无法实现的。在一系列光活性材料中，我们首次证明了光致变色化合物的光异构化速率可以在近 2 个数量级内进行调节。此外，光响应衍生物的环化速率可以作为框架结构的函数进行调节。此外，通过 MOF 工程，我们能够实现配位固定的螺吡喃衍生物的完全异构化，通常在固态下表现出有限的光开关行为。例如，光谱分析表明，接枝到 MOF 支柱骨架上的新型单取代螺吡喃衍生物表现出显著的光异构化速率，为 0.16 s，与溶液中环化的典型速率相当。我们还将获得的基本原理应用于材料性能变化的映射，这可能为监测材料老化或结构恶化提供一种途径。
