Qian Yunyang, Li Dandan, Han Yulan, Jiang Hai-Long
Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China.
Institutes of Physics Science and Information Technology, Anhui University, Hefei 230601, P.R. China.
J Am Chem Soc. 2020 Dec 9;142(49):20763-20771. doi: 10.1021/jacs.0c09727. Epub 2020 Nov 23.
Excitonic effects caused by Coulomb interactions between electrons and holes play subtle and significant roles on photocatalysis, yet have been long ignored. Herein, porphyrinic covalent organic frameworks (COFs, specifically DhaTph-M), in the absence or presence of different metals in porphyrin centers, have been shown as ideal models to regulate excitonic effects. Remarkably, the incorporation of Zn in the COF facilitates the conversion of singlet to triplet excitons, whereas the Ni introduction promotes the dissociation of excitons to hot carriers under photoexcitation. Accordingly, the discriminative excitonic behavior of DhaTph-Zn and DhaTph-Ni enables the activation of O to O and O, respectively, under visible light irradiation, resulting in distinctly different activity and selectivity in photocatalytic terpinene oxidation. Benefiting from these results, DhaTph-Ni exhibits excellent photocatalytic activity in O-engaged hydroxylation of boronic acid, while DhaTph-Zn possesses superior performance in O-mediated selective oxidation of organic sulfides. This work provides in-depth insights into molecular oxygen activation and opens an avenue to the regulation of excitonic effects based on COFs.
电子与空穴之间的库仑相互作用所引起的激子效应在光催化过程中发挥着微妙而重要的作用，但长期以来一直被忽视。在此，卟啉共价有机框架（COFs，特别是DhaTph-M），在卟啉中心存在或不存在不同金属的情况下，已被证明是调节激子效应的理想模型。值得注意的是，在COF中引入锌有助于单线态激子向三线态激子的转化，而引入镍则促进激子在光激发下解离为热载流子。因此，DhaTph-Zn和DhaTph-Ni的判别性激子行为分别在可见光照射下实现了O到O和O的活化，从而在光催化萜品烯氧化中产生明显不同的活性和选择性。受益于这些结果，DhaTph-Ni在硼酸的O参与羟基化反应中表现出优异的光催化活性，而DhaTph-Zn在有机硫化物的O介导选择性氧化中具有卓越的性能。这项工作为分子氧活化提供了深入的见解，并开辟了一条基于COFs调节激子效应的途径。
