Synthetic chemistry is the art of molecules.By breaking and forming chemical bonds,chemists can transform one molecule into another,and provide a variety of chemicals that we use in our daily lives.Among all chemical bonds,the carbon-hydrogen (C-H) bond is one of the most common,and is present in almost every organic compound.Breaking C-H bonds and connecting the carbon atoms with other atoms or groups is an essential step for the synthesis of a large variety of chemicals—from bulk chemicals to functional materials and drug candi-dates.However,the C-H bond is extremely stable and difficult to break,and C-H activation and functionalization has been a challenging fundamental problem for decades.