复旦大学郭佳团队报道了调控共价有机框架的光异构化促进光催化析氢。相关研究成果于2024年7月3日发表在《中国化学》。

共价有机框架（COF）是一个理想的调整电子性能以提高光催化性能的平台。然而，对决定光生载流子动力学的激发态构型的研究长期以来一直被忽视。

该文中，研究人员专注于β-酮烯胺连接的COFs的分子设计，通过激发态分子内质子转移（ESIPT）驱动其光异构化，从而诱导部分酮到烯醇的互变异构，并相应地重新排列光诱导的电荷分布。研究人员证明了连接在框架连接体上的功能性侧基的推挽电子效应与ESIPT过程直接相关。用吸电子氰基修饰的亚苯基连接体增强了ESIPT诱导的互变异构化，导致原位部分烯醇化以扩展π-共轭和重排电子-空穴分布。

相反，富含电子的连接体限制了COF的光异构化，并抑制了光诱导的电子积累。因此，氰基改性的COFs实现了最大的析氢速率，高达162.72mmol·g^–1·h^–1，在475 nm处的表观量子效率为13.44%，几乎是具有富电子连接体的类似COF的11.5倍。

该工作为控制增强光化学应用的激发态结构转变开辟了一条途径。

附：英文原文

Title: Regulating the Photoisomerization of Covalent Organic Framework for Enhanced Photocatalytic Hydrogen Evolution†

Author: Xingye Huang, Jia Guo

Issue&Volume: 2024-07-03

Abstract: Covalent organic framework (COF) is a desirable platform to tailor electronic properties for improving photocatalytic performances. However, the study on excited-state configurations that determine photogenerated carrier dynamics has long been neglected. Herein, we concentrate on the molecular design of β-ketoenamine-linked COFs to drive their photoisomerization via the excited-state intra-molecular proton transfer (ESIPT), which can induce the partial keto-to-enol tautomerization and accordingly rearrange the photoinduced charge distribution. We demonstrate that the push-pull electronic effect of functional side groups attached on the framework linkers is directly correlated with the ESIPT process. The phenylene linkers modified with electron-withdrawing cyano-groups reinforce the ESIPT-induced tautomerization, leading to the in situ partial enolization for extended π-conjugation and rearranged electron-hole distribution. In contrast, the electron-rich linkers limit the photoisomerization of COF and suppress the photoinduced electron accumulation. Thus, the maximum hydrogen evolution rate is achieved by the cyano-modified COF, reaching as high as 162.72mmol·g–1·h–1 with an apparent quantum efficiency of 13.44% at 475 nm, which is almost 11.5-fold higher than those of analogous COFs with electron-rich linkers. Our work opens up an avenue to control over the excited-state structure transformation for enhanced photochemical applications.

DOI: 10.1002/cjoc.202400437

Source: https://onlinelibrary.wiley.com/doi/full/10.1002/cjoc.202400437