直接Z-Scheme异质结Al-PMOFs/CdZnS光催化剂的制备及其光催化苯甲胺氧化性能

Preparation and photocatalytic properties of direct Z-Scheme heterojunction Al-PMOFs/CdZnS photocatalysts for benzoylamine oxidation

摘要:

摘要：采用水热法合成了具有立方柱状结构的卟啉基金属有机框架化合物(Al-PMOFs)，然后通过共沉淀法将CdZnS纳米颗粒沉积在Al-PMOFs棱柱上，得到了界面接触良好的异质结Al-PMOFs/CdZnS纳米杂化材料。将催化剂应用于可见光催化苯甲胺氧化偶联反应中，结果表明，Al-PMOFs/CdZnS纳米复合材料具有较好的光催化反应活性和稳定性。室温下当溶剂为N,N-二甲基甲酰胺(DMF)时，经可见光照射7 h后，苯甲胺可以发生氧化偶联反应生成N-苄基-1-苯基甲亚胺(BPMI)，苯甲胺的转化率可达97%，BPMI 的选择性超过99%，复合材料的光催化活性较相同条件下单一的CdZnS和Al-PMOFs提高了2倍。Al-PMOFs/CdZnS光催化性能的提高主要归因于Al-PMOFs与CdZnS之间形成了直接Z-scheme异质结，该异质结能够促进Al-PMOFs和CdZnS界面上的电荷传输，抑制Al-PMOFs/CdZnS杂化材料表面光生载流子的复合。通过自由基捕获实验等提出了适合该体系的直接Z-scheme光催化反应机理以及电荷转移路径。

Abstract:

Abstract: Porphyrin-based metal organic framework compounds (Al-PMOFs) with cubic columnar crystal structure were synthesized by hydrothermal method. CdZnS nanoparticles were prepared and deposited on the surface of Al-PMOFs cubic columns by chemical coprecipitation, Al-PMOFs/CdZnS nanohybrid materials with good interfacial contact were obtained. The photocatalytic activity of the prepared Al-PMOFs/CdZnS nanohybrids were evaluated by the photooxidative coupling reaction of benzylamine. The results show that Al-PMOFs/CdZnS nanocomposites have excellent photocatalytic activity and stability for the reaction. When N,N-dimethylformamide (DMF) was the solvent at room temperature, after a 7-hour-irridiation of visible light, Benzylamine can be oxidized to form n-benzyl-1-phenylmethylimine (BPMI). The conversion rate of benzylamine can reach 97%, and the selectivity of BPMI is higher than 99%. The photocatalytic activity of Al-PMOFs/CdZnS nanohybrids is 2 times higher than that of each pure component of CdZnS or Al-PMOFs, and photoactivity of the prepared Al-PMOFs/CdZnS nanohybrids can also be extended to the photooxidative coupling of many other benzylamine derivatives. The improvement of the photoactivity of Al-PMOFs/CdZnS nanohybrid materials is mainly due to the formation of Z-scheme heterojunction between Al-PMOFs and CdZnS. After many careful characterizations and analyses, it is proved that the Z-scheme heterojunction can efficiently promote the charge transfer at the interface between Al-PMOFs and CdZnS and inhibit the recombination of the photogenerated carriers on the surface of Al-PMOFs/CdZnS nanohybrids. The probable mechanism as well as the route for the transfer of the photogenerated carriers for this photocatalytic system was proposed by free radical trapping experiment.