Photochemical reaction dynamics of molecules adsorbed into zeolites as revealed by time-resolved spectroscopic techniques.

1.荧光光谱法研究芳烃与分子筛的相互作用荧光光谱结果表明，蒽在分子筛上的吸附行为与分子筛的负载量、分子筛的水合状态以及分子筛的化学组成有关。蒽分子被认为与脱水NaX和NaY沸石骨架中的Na^+离子络合，并且在高负载水平下。它们在Na^+离子的影响下形成二聚体。此外，我们的荧光光谱研究表明，在大量的水和其他溶剂分子的存在下，在相对高的负载量的蒽晶体的形成。因此，我们发现，在沸石超笼内的客体芳族分子的动态行为严重依赖于沸石骨架，客体物种和共吸附物之间的相互作用的平衡。特别是共吸附的水。共吸附SO的影响 ...更多信息 我们发现，在足够低的蒽负载水平下，衰减速率取决于水、甲醇和吡啶的量，但几乎不受正己烷的影响。增强的三重态衰变率被认为是由于自猝灭事件，即基态蒽的三重态猝灭。因此，给出了一幅图片，蒽分子是高度移动的时，沸石空腔负载的共吸附溶剂的量足以屏蔽阳离子位点，蒽是应该被吸附。客体物种的高流动性可能是由于蒽与沸石壁的吸附相互作用通过少量对沸石框架具有强亲和力的溶剂分子的作用而释放。相反，大量的共吸附溶剂预计会干扰笼网络中蒽的运动，因为它们是如此拥挤，足以填充笼之间的互连窗口以及笼体积的大部分。分子筛中的分子扩散系数本文提出了一种基于光化学的新的实验方法，用于测定吸附在分子筛中的芳烃物种的扩散常数。该技术基本上观察由脉冲激光照射产生的激发探针的淬灭动力学。预期探针分子或者失活或者通过在笼形网络内迁移的另一分子（猝灭剂）经历猝灭。采用CTRW（连续时间随机游走）模型对猝灭动力学进行了分析。除了对蒽和甘菊环在NaY中的扩散系数进行估计之外，本研究还表明了居住在相邻笼中的分子之间的长程反应的指示，反映了笼网络的开放结构。少

1. Flurescence Spectroscopic Investigation of the Interaction of aromatics with ZeolitesThe fluorescence spectroscopic results revealed a remarkable behavior of anthracene adsorbed into zeolites depending on the loading level and the state of hydration of the zeolites as well as the chemical composition of the zeolites. Anthracene molecules are suggested to be complexed with Na^+ ions in the zeolite frameworks of dehydrated NaX and NaY, and at high loading levels. they form dimers under the influence of Na^+ ion. Additionally, our fluorescence spectroscopic investigation revealed the formation of anthracene crystals at relatively high loadings in the presence of a large amount of water and other solvent molecules. Thus we found that the dynamic behavior of the guest aromatic molecules within the zeolite supercages are critically dependent upon the balance of interactions among the zeolite frameworks, guest species and coadsorbates. especially coadsorbed water.2. Effect of Coadsorbed So … More lventsWe found that at a sufficiently low loading level of anthracene the decay rate is dependent on the amount of water, methanol and pyridine but scarcely affected by n-hexane. The enhanced triplet decay rate was found to be ascribable to a self-quenching event, i.e. the triplet quenching by ground-state anthracene. Thus a picture was given that anthracene molecules are highly mobile when the zeolite cavities are loaded with the coadsorbed solvents in quantities sufficient to shield the cationic sites at which anthracene is supposed to be adsorbed. The high mobility of the guest species is presumably caused by the liberation of adsorption interaction of anthracene with the zeolite walls by the action of small quantities of the solvent molecules with strong affinity towards the zeolite frameworks. On the contrary, large quantities of the coadsorbed solvens are expected to interfere with the movement of anthracene in the cage networks because they are so crowded enough to fill the interconnecting windows between cages as well as a large portion of the cage volume.3. Molecular Diffusivity in ZeolitesWe present a new experimental technique based on photochemistry for acquiring diffusion constants of aromatic species adsorbed in zeolites. The technique basically observes the quenching kinetics of excited probes produced by the pulsed-laser irradiation. The probe molecules are expected either to deactivate or to undergo quenching by another molecule (a quencher) migrating within the cage networks. The quenching kinetics were analyzed by applying the CTRW (continuous time random walk) model. In addition to the estimation of the diffusion coefficient for anthracene and azulene in NaY, the present study showed the indication of the long-range reaction between molecules residing in the neighboring cages, reflecting open structure of the cage network. Less