中国科学技术大学江海龙课题组近日提出了通过调节激子效应在共价有机框架（COF）中实现光催化分子氧活化。 相关论文于2020年11月23日发表于国际顶尖学术期刊《美国化学会志》。

在该研究中，卟啉基的共价有机框架化合物（尤其是DhaTph-M）通过卟啉中心存在或缺失不同金属原子，被作为调控激子效应的理想模型。值得注意的是，COF中Zn²⁺的加入促进了单线态激子向三线态激子的转变，而Ni²⁺的引入促进了激子在光激发下解离为热载流子。相应的，DhaTph-Zn和DhaTph-Ni激子行为的差别使O2在可见光照射下分别活化为¹O₂和O₂^·-，导致在光催化下萜品烯氧化反应的活性和选择性明显不同。

利用以上发现，DhaTph-Ni在O₂^·-参与的硼酸的羟基化反应中表现出优秀的光催化活性，而DhaTph-Zn则在¹O₂介导的有机硫化物选择性氧化反应中表现优异。这项工作为分子氧激活提供了深入的见解，并为基于COF的激子效应调节开辟了一条途径。

据了解，电子和空穴之间的库仑相互作用产生的激子效应在光催化中起着微妙而重要的作用，但长期以来一直被人们忽略。

附：英文原文

Title: Photocatalytic Molecular Oxygen Activation by Regulating Excitonic Effects in Covalent Organic Frameworks

Author: Yunyang Qian, Dandan Li, Yulan Han, Hai-Long Jiang

Issue&Volume: November 23, 2020

Abstract: 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 Zn2+ in the COF facilitates the conversion of singlet to triplet excitons, whereas the Ni2+ 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 O2 to 1O2 and O2–, 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 O2–-engaged hydroxylation of boronic acid, while DhaTph-Zn possesses superior performance in 1O2-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.

DOI: 10.1021/jacs.0c09727

Source: https://pubs.acs.org/doi/10.1021/jacs.0c09727