P掺杂C_(3)N_(4)的制备及其在碱催化反应中的应用

Facile Synthesis of P-doped C_(3)N_(4) for Base-catalyzed Reactions

基于酸碱协同催化设计思想,以结构类似的三聚氰胺和六氯环三磷腈热缩聚制备了P掺杂的C_(3)N_(4)材料。利用SEM和BET分析P掺入前后材料的结构,发现P掺入后材料变为直径约为5μm的球状结构,比表面积由8.2 m^(2)/g增加至11.9 m^(2)/g。采用XPS和^(31)P MAS NMR证明P以P-OH和P=O键形式进入三嗪结构骨架中。将P掺杂的C_(3)N_(4)材料作为无金属多相催化剂应用于碱催化反应中。采用硝酸将部分P-OH氧化为P=O,探讨了P种类和数量对环氧丙烷与CO_(2)环加成反应、碳酸丙烯酯与甲醇酯交换反应以及苯甲醛与丙二腈Knoevenagel反应的影响,结合XPS和^(31)P MAS NMR表征结果发现P-OH的引入有利于CO_(2)环加成反应、酯交换反应和Knoevenagel反应的进行。

Based on the synergic catalytic effects between Base and Acid,P doped carbon nitride were facilely synthesized by thermal polycondensation of hexachlorotriphosphazene and melamine.Based on the results of SEM and BET analyses,P-C_(3)N_(4)show a spheroidal structure with 11.9 m^(2)/g.As characterized by XPS and^(31)P MAS NMR analyses,there is substitution of P atoms for C atoms which located at the bay and edge terminal positions.Partial P-OH bonds of P doped carbon nitride were oxidized to P=O by HNO_(3).The P doped carbon nitride was used as easy-to-handle and metal-free heterogeneous catalyst for base-catalyzed reactions such as cycloaddition of CO_(2)with propylene oxide,transesterification of propylene carbonate with methanol,Knoevenagel reaction between benzaldehyde and malononitrile.The relation between catalytic performance and the type and amount of P were investigated.The excellent performance of P-C_(3)N_(4)for CO_(2)cycloaddition,transesterification and Knoevenagel reaction is owing to the synergetic effect of P-OH and uncondensed amino groups.