Rapid Exciton Transport and Structural Defects in Individual Porphyrinic Metal Organic Framework Microcrystals
Rapid Exciton Transport and Structural Defects in Individual Porphyrinic Metal Organic Framework Microcrystals
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单个卟啉金属有机骨架微晶体中的快速激子输运和结构缺陷
DOI：
10.1021/jacs.3c12275
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发表时间：
2024-02
影响因子：
15
通讯作者：
S. Afrin;Xiaozhou Yang;Amanda J Morris;Erik M. Grumstrup
中科院分区：
文献类型：
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作者：
S. Afrin;Xiaozhou Yang;Amanda J Morris;Erik M. Grumstrup
迄今为止，基于卟啉的金属有机框架（MOFs）的光谱表征几乎完全依赖于集成技术，它只提供结构平均洞察这些有前途的光化学平台的功能特性。这项工作采用时间分辨泵浦-探测显微镜探测超快动力学在PCN-222 MOF单晶。同时高的空间和时间分辨率的技术，使相关的光谱观测到晶体间和晶体内的结构异质性。泵浦-探测测量表明，在激发态寿命的显着差异存在于单个PCN-222晶体的合奏。在单个PCN-222晶体上，发现激发态寿命和光致发光量子产率的差异与结晶时引入的微尺度结构缺陷相关。泵浦探针显微镜还能够直接测量激发态传输。单个MOF晶体上的激子运输的成像揭示了快速，但subdiffusively激子运输减慢ps时间尺度上的10秒。在第一个200 ps的时间平均激子扩散系数跨越0.27至1.0 cm 2/s的范围内，表明激发态被迅速运输通过的卟啉网络的PCN-222之前被捕获。总之，这些单粒子分辨的测量提供了重要的新的洞察所发挥的作用的结构缺陷的光化学功能的卟啉为基础的MOFs。
To date, spectroscopic characterization of porphyrin-based metal organic frameworks (MOFs) has relied almost exclusively on ensemble techniques, which provide only structurally averaged insight into the functional properties of these promising photochemical platforms. This work employs time-resolved pump–probe microscopy to probe ultrafast dynamics in PCN-222 MOF single crystals. The simultaneous high spatial and temporal resolution of the technique enables the correlation of spectroscopic observables to both inter- and intracrystal structural heterogeneity. The pump–probe measurements show that significant differences in the excited state lifetime exist between individual PCN-222 crystals of an ensemble. On a single PCN-222 crystal, differences in excited state lifetime and photoluminescence quantum yield are found to correlate to microscale structural defects introduced at crystallization. Pump probe microscopy also enables the direct measurement of excited state transport. Imaging of exciton transport on individual MOF crystals reveals rapid, but subdiffusive exciton transport which slows on the 10s of ps time scale. Time-averaged exciton diffusion coefficients over the first 200 ps span a range of 0.27 to 1.0 cm2/s, indicating that excited states are rapidly transported through the porphyrin network of PCN-222 before being trapped. Together, these single-particle-resolved measurements provide important new insight into the role played by structural defects on the photochemical functionality of porphyrin-based MOFs.