共价有机骨架上锚定单原子活性位点用于高效的金属化光氧化还原C–N交叉偶联

Engineering single–atom active sites anchored covalent organic frameworks for efficient metallaphotoredox C-N cross–coupling reactions

光氧化还原催化是一种在温和条件下实现可持续有机转化、建立绿色化学产业的有效方法.光氧化还原/过渡金属双催化C–N能够获得大量有价值的材料、药物和多功能的精细化学品.通过在共价有机骨架上(COF)精确构建单原子活性位点不仅能提高催化性能,而且有助于对其构效关系的理解.本文发展了一种锚定Ni单原子的COF(Ni SAS/TD-COF).利用XANES和EXAFS研究了过渡金属镍的配位环境.Ni SAS/TD-COF催化剂在温和的条件下实现了芳基溴与胺的可见光催化C–N交叉偶联反应.该异质催化体系对于缺电子、富电子和中性基团的33种底物均能得到良好的产率.异质Ni SAS/TD-COF催化剂可以很容易地从反应混合物中回收.这项工作对于合理设计COF基光催化剂用于有机物转化提供新思路.

Photoredox catalysis has become an indispensable solution for the synthesis of small organic molecules.However,the precise construction of single-atomic active sites not only determines the catalytic performance,but also avails the understanding of structure–activity relationship.Herein,we develop a facile approach to immobilize single-atom Ni sites anchored porous covalent organic framework(COF)by use of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,6-diformylpyridine(Ni SAS/TD-COF).Ni SAS/TDCOF catalyst achieves excellent catalytic performance in visible-light-driven catalytic carbon–nitrogen cross-coupling reaction between aryl bromides and amines under mild conditions.The reaction provides amine products in excellent yields(71%–97%)with a wide range of substrates,including aryl and heteroaryl bromides with electron-deficient,electron-rich and neutral groups.Notably,Ni SAS/TD-COF could be recovered from the reaction mixture,corresponding to the negligible loss of photoredox performance after several cycles.This work provides a promising opportunity upon rational design of single-atomic active sites on COFs and the fundamental insight of photoredox mechanism for sustainable organic transformation.