Design And Synthesis Of Cu/N-C Materials And Catalytic Activation Of Heteroatom α-position

Graphite-phase carbon nitride,typified by g-C₃N₄,is a type of semiconductor conjugated polymer materials with visible light response,which was easily prepared and has high physical&chemical stabilities as well as excellent photocatalytic performance.However,this material also suffers from some defects,such as lower specific surface area,narrow absorption band in visible light,and a high recombination rate of photogenerated electron–hole pairs,which usually lead to poor catalytic efficiency in actual chemical reactions.On the other hand,Group IB metal nanoparticles can be utilized as efficient photocatalyst because of their strong localized surface plasmon resonance effect（LSPR）,smaller particle size,and higher specific surface area.Herein,we designed and prepared a novel graphite-phase carbonitride material with different precursors to modify their semiconductor properties.Moreover,the Group IB metal nanoparticles were then combined with the novel carbonitride material in order to prepare a highly efficient photocatalyst for organic reactions under visible light irradiation.Heteroatoms（N,O,S,P et.）exist widely in natural organic compounds,and heteroatom-containing drugs account for the largest proportion in synthetic drugs.The nitrogen or oxygen atom in organic compounds could undergo a single-electron oxidation to generate free radical cations,and result in the activation of the C-H bond adjacent to the heteroatoms via a deprotonation process to forma-carbon free radical.Subsequently,a series of organic synthesis reactions could be derived through the coupling or transfer of the free radicals.The regular strategy to achieve this single-electron oxidation process is to use a combination system of cuprous salt and TBHP,or undergo a homogeneous photocatalytic system with noble metal photocatalysts.However,the current methodologies usually require a quantitative oxidant,and the catalyst is difficult to recycle.Therefore,researching and developing a series of environmentally friendly heterogeneous catalytic systems is a very meaningful project.Thus,we hope to achieve the same single-electron oxidation process on the valence band holes generated from our novel metal-carbonitride nanocomposite under visible light instead.In this paper,a nano-network N-C material（C:N=2:3）was designed and synthesized with melamine and 3,6-dichloro-1,2,4,5-hepta tetrazine as precursors in acetonitrile via a solvothermal method,and then,Cu-NPs were supported on the N-C material by liquid-phase reduction.The novel N-C material and its copper nanopartical composite were characterized by element analysis,TEM,XPS,XRD,and UV-vis DRS test.A nano-network structure was observed from the N-C material,and the Cu/N-C composite also maintains the morphology of the N-C material.Compared with bulk C₃N₄ and g-C₃N₄,the visible light absorption band of the N-C material I was significantly broadened,which might suggest better photophysical properties than that of the two others.With the Cu/N-C nanocomposite as a photocatalyst&oxygen as oxidant,the selective cleavage of C-C single bond between theα-carbon andβ-carbon of the nitrogen atom in amine compounds was achieved at room temperature under blue light irradiation in acetonitrile solvent.The carbon-carbon single bond was oxidatively cleaved into two formyl groups in good yields.Based on the similar mechanism,a highly efficient formylation of secondary amines was also developed with Cu/N-C as the photocatalyst and phenylacetaldehyde as the formylating agent,under blue light in acetone solvent at room temperature.Under oxygen atmosphere,the reaction occurred smoothly and good to excellent yields were achieved.