As complex materials are widely used in emerging technologies for environmental and energy applications, it is important to be able to quantify their stimuli-response behaviors. Light is a useful stimulus to modulate multifunctional electrochemical, magnetic, optical, and structural properties in metal–organic frameworks (MOFs); however, the underlying mechanisms and kinetics of light-induced structural changes are not well understood. Herein, a double [2 + 2] photocyclization in photoactive [Cd₂(stil)₂(Py₂TTF)₂] (stil^2– = 4,4′-stilbenedicarboxylic acid, Py₂TTF = 2,6-bis(4′-pyridyl)-tetrathiafulvalene) offers a powerful platform to quantitatively probe solid-state photocyclization kinetics. Variable-temperature Raman spectroscopy revealed a nonlinear temperature dependence of these parameters, which could be analyzed using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model to yield a maximum rate observed between 0 °C and 20 °C of approximately 0.172 s^–1. These results offer the first example of the quantification of the photocyclization kinetics in a MOF. Density functional theory (DFT) calculations support a singlet reaction mechanism for the double [2 + 2] photocyclization, which is facilitated by the cofacial alignment of Py₂TTF ligands. Establishing mechanistic and kinetic models that can be applied to multistimuli-responsive materials provides a powerful platform for their future design for applications in sensing, switching, and molecular separations.

中文翻译：

---

光环化动力学的量化及其在共面金属-有机骨架中的温度依赖性

由于复杂材料广泛用于环境和能源应用的新兴技术，因此能够量化其刺激响应行为非常重要。光是调节金属有机框架 (MOF) 中多功能电化学、磁性、光学和结构特性的有用刺激；然而，光诱导结构变化的潜在机制和动力学尚不清楚。_{在此，光活性 [Cd 2} (stil) ₂ (Py ₂ TTF) ₂ ] (stil ^2– = 4,4'-茋二甲酸，Py ₂ ) 中的双 [2 + 2] 光环化TTF = 2,6-bis(4'-pyridyl)-tetrathiafulvalene) 提供了一个强大的平台来定量探测固态光环化动力学。变温拉曼光谱揭示了这些参数的非线性温度依赖性，可以使用 Johnson–Mehl–Avrami–Kolmogorov (JMAK) 动力学模型对其进行分析，以产生在 0 °C 和 20 °C 之间观察到的最大速率，约为 0.172 秒^–1。这些结果提供了 MOF 中光环化动力学量化的第一个例子。密度泛函理论 (DFT) 计算支持双 [2 + 2] 光环化的单线态反应机制，这由 Py _{2的共面排列促进}TTF配体。建立可应用于多刺激响应材料的机械和动力学模型为其未来在传感、开关和分子分离方面的应用设计提供了一个强大的平台。