共价有机框架-杂多酸复合材料用于非均相催化烯烃环氧化

Application of Covalent Organic Framework-Polyoxometalates Composites in Heterogeneous Catalytic Epoxidation of Olefins

共价有机骨架是一种结晶性多孔材料,在非均相催化方面有着巨大的应用潜力.本文利用缺电子结构萘二酰亚胺(NDI)的衍生物作为单体,合成了一种新型功能性共价有机框架材料COF-FL-2.COF-FL-2具有较大的孔径和良好的吸附性能,骨架上的NDI结构能通过π-阴离子作用与杂多酸形成稳定的功能性复合材料.通过将磷钨酸(PTA)负载在COF-FL-2上,进一步制备了一种新型杂化杂多酸基复合物PTA@COF-FL-2.PTA@COF-FL-2对以过氧化叔丁醇(t-BuOOH)为氧化剂的烯烃环氧化反应表现出高的催化活性,可以在温和的条件下将环辛烯和1-辛烯环氧化成相应的环氧化物.PTA@COF-FL-2具有出色的稳定性,在反应条件下可长期使用,使用时无PTA浸出现象.此外,PTA@COF-FL-2回收非常方便,可以多次循环使用.

Covalent organic frameworks are crystalline porous materials with great application potential in heteroge⁃neous catalysis.We synthesized a new functional covalent organic framework,COF-FL-2,using derivatives of electron-deficient naphthalene diimide(NDI)as monomers.COF-FL-2 has a large pore size and good adsorption performance.The NDI structure on the skeleton can form a stable functional composite with polyoxometalates through π-anion interaction.A novel hybrid heteropolyacid complex,PTA@COF-FL-2,was prepared by loading phosphotungstic acid(PTA)on COF-FL-2.Remarkably,PTA@COF-FL-2 shows high catalytic activity for the epoxidation of olefins with t-BuOOH as the oxidant,and can epoxidate cyclooctene and 1-octene into the corresponding epoxides under mild conditions.PTA@COF-FL-2 can be used for a long time under reaction conditions,and there is no PTA leaching phenomenon when used.In addition,PTA@COF-FL-2 is very convenient to recycle and can be recycled many times.