Recently, Professor Lanyaqian's team from the School of Chemistry at South China Normal University published their latest research progress in "Angewandte Chemie International Edition". They reported for the first time the achievement of photo-thermal heterogeneous C-H activation reaction by combining covalent organic framework materials and transition metal rhodium clusters through a post-synthetic method.
In recent years, transition metal-catalyzed C-H bond activation reactions have become important synthetic strategies in organic synthesis due to their step and atom economy. However, these reactions often require high temperatures. Many recent studies have focused on developing more environmentally friendly and resource-saving methods to achieve these reactions under mild conditions. Among them, photocatalysis is an environmentally friendly alternative, providing a milder pathway for thermally driven reactions by transferring absorbed light energy or electrons.
Covalent organic frameworks are a class of crystalline porous organic materials with characteristics such as good chemical and thermal stability, as well as tunability, making them potential candidates for heterogeneous photocatalysts. The rate-determining step for the majority of C-H activation reactions depends on the breaking process of highly thermodynamically stable C-H bonds. Therefore, there is a need to develop a type of covalent organic framework composite material capable of generating photo-thermal effects to promote the C-H bond breaking step and thus drive the C-H activation reaction cycle.
Based on this, Professor Lanyaqian's team achieved photo-thermal catalytic C-H activation by modifying the catalysts to possess both photosensitive properties and transition metal catalytic sites. They designed and synthesized two composite materials based on covalent organic frameworks, Rh-COF-316 and -318, for heterogeneous photo-thermal C-H activation reactions.
Benefiting from the ordered structure of covalent organic frameworks and the covalent bonding mode of cyclopentadiene rhodium segments, Rh-COF with uniformly distributed Rh-COF was spontaneously formed using a programmable method based on the retained carboxyl groups in the covalent organic framework. Compared with homogeneous C-H activation reactions, the Rh-COF catalysts in heterogeneous reactions can simultaneously play a dual-function role. With these advantages, Rh-COF catalysts exhibit excellent catalytic yields (up to 98%), a wide range of substrates, high stability, and good reusability.
This work not only expands the application of covalent organic framework-based complexes in photocatalytic C-H activation reactions but also verifies the universality and feasibility of obtaining heterogeneous catalysts through post-synthetic transition metal clusters. Therefore, this strategy holds great promise for promoting the utilization of functional covalent organic framework materials in multiphase catalysis and may even advance their industrial applications.
Related Paper Information: https://doi.org/10.1002/anie.202318180
