ALiCE-Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
LSRE-LCM - Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto s/n, 4200-465 Porto, Portugal.
Molecules. 2022 Feb 15;27(4):1295. doi: 10.3390/molecules27041295.
Vitamin B3 (nicotinic acid, VB3) was synthesized through the photocatalytic oxidation of 3-pyridinemethanol (3PM) under visible-light-emitting diode (LED) irradiation using metal-free graphitic carbon nitride (GCN) - based materials. A bulk (GCN) material was prepared by a simple thermal treatment using dicyandiamide as the precursor. A post-thermal treatment under static air and nitrogen flow was employed to obtain the GCN-T and GCN-T-N materials, respectively. The conditions adopted during the post-treatment revealed differences in the resulting materials' morphological, electronic, and optical properties. The post-treated photocatalysts revealed an enhanced efficiency in the oxidation of 3PM into VB3, with the GCN-T-N photocatalyst being the best-performing material. The defective surface, reduced crystallinity, and superior photoabsorption of GCN-T-N account for this material's improved performance in the production of VB3. Nevertheless, the presence of nitrogen vacancies in the carbon nitride structure and, consequently, the creation of mid-gap states also accounts to its highly oxidative ability. The immobilization of GCN-T-N in sodium alginate hydrogel was revealed as a promising strategy to produce VB3, avoiding the need for the photocatalyst separation step. Concerning the mechanism of synthesis of VB3 through the photocatalytic oxidation of 3PM, it was possible to identify the presence of 3-pyridinecarboxaldehyde (3PC) as the intermediary product.
烟酸（VB3）是通过在可见光发光二极管（LED）照射下，使用无金属石墨相氮化碳（GCN）基材料光催化氧化 3-吡啶甲醇（3PM）合成的。采用二氰胺作为前驱体，通过简单的热处理制备块状（GCN）材料。在静态空气和氮气流下进行后热处理，分别得到 GCN-T 和 GCN-T-N 材料。后处理条件的差异导致所得材料的形态、电子和光学性质不同。后处理的光催化剂在将 3PM 氧化成 VB3 的过程中表现出更高的效率，其中 GCN-T-N 光催化剂的性能最佳。GCN-T-N 的缺陷表面、结晶度降低和优异的光吸收解释了其在 VB3 生产中的性能提高。然而，氮化碳结构中氮空位的存在以及由此产生的带隙中间态也使其具有很强的氧化能力。将 GCN-T-N 固定在海藻酸钠水凝胶中被证明是一种生产 VB3 的有前途的策略，避免了光催化剂分离步骤的需要。关于通过 3PM 的光催化氧化合成 VB3 的机制，可以确定 3-吡啶甲醛（3PC）是中间产物。
