Preparation Of Ag/g-C₃N₄ Composite And Its Utilization In Synthetic Reactions Under Visible Light

Since the increasing problems of environmental pollution caused by industrial production, developing green, energy-saving and efficient organic chemical reaction has been widely concerned. The utilization of visible light to drive organic reactions provides a sustainable pathway for green synthesis and attracted significant interest in recent years. Recently, g-C₃N₄ as a kind of novel organic polymer semiconductor material, has been widely reported as nanoparticles carrier, gas adsorption medium and non-metal catalyst, becase of its unique semiconductor electronic band structure and excellent chemical stability. g-C₃N₄ has also been used as photocatalytic material becase of its unique properties such as visible responded, high chemical and thermal stability, environmental compatibility. However, its small specific surface area and low quantum yield restrict the photocatalytic efficiency of g-C₃N₄ seriously. On the other hand, IB metal nanoparticles were found to exist strong interaction with resonant incident photons through excitation of the localized surface plasmon resonance（LSPR）, and were recognized as a new form of medium that is particularly efficient in harvesting light energy for chemical processes due to their strong light absorption over a wide range of the visible and UV regions of the solar spectrum. However, there are few reports on their utilization as photocatalyst for organic synthesis reactions under visible light irradiation.In this dissertation, an Ag/g-C₃N₄ nanocomposite was synthesized and utilized as an efficient and green photocatalyst for oxidative amidation of aldehydes under visible light irradiation. The combination of Ag NPs and g-C₃N₄, provides a novel strategy to enhance the photocatalytic performance of g-C₃N₄.Firstly, we synthesized layered g-C₃N₄ material by a modified method with melamine and cyanuric chloride as precursor, and first demonstrated the synthesis of Ag/g-C₃N₄ hybrid material by a facile impregnation-roasting method.Then, the material was characterized by EA, BET, HRTEM, XRD, XPS, UV-vis and PL. The analysis results showed that g-C₃N₄ possess C/N molar ratio approach 0.73, with a pore size distribution in 2-5 nm, specific surface area is 34 m²/g, band gap of g-C₃N₄ and Ag/g-C₃N₄ are 1.98 eV and 1.91 eV, respectively.Finally, the Ag/g-C₃N₄ nanocomposite showed superior photocatalytic performance toward aerobic oxidative amidation of aromatic aldehydes under visible light irradiation. The inexpensive, stable g-C₃N₄ coupled with the localized surface plasmon resonance（LSPR） effect of Ag NPs, exhibited high catalytic activity in the reaction. Good to excellent yields were achieved for various substrates under the light of a 25 W CFL. Furthermore, the catalyst could be recycled effectively.In summary, the Ag/g-C₃N₄ material was prepared by a facile method, which showed a good catalytic activity in the oxidative amidation of aldehydes. The reaction showed good functional group tolerance and wide substrates scope under the mild reaction conditions.