Synthesis and characterization of a new epoxidation catalyst by grafting cis-MoO2(salpr) complex to functionalized MCM-41

The mesoporous molecular sieve MCM-41 was covalently grafted with 3-chloropropyl trimethoxylsilane and was then reacted with N,N′-bis(3-salicylidenaminopropyl)amine(salpr) to afford MCM-41 containing salpr ligand, salpr/Si-MCM-41. Powder X-ray diffraction and nitrogen adsorption–desorption analyses revealed that not only the textural characteristics of the support were preserved during the grafting experiments but also the channels remained accessible despite sequential reduction in surface area, pore volume and pore size. The salpr/Si-MCM-41 material was then reacted with MoO2(acac)2 to give MoO2(salpr)/Si-MCM-41 catalyst with molybdenum loading of 1.75 wt.%. The molybdenum-containing MCM-41 was shown to successfully catalyze the epoxidation of 1-hexene, 1-octene, cyclohexene and cyclooctene with tert-butylhydroperoxide (TBHP) quantitatively with 95–99% selectivity toward the corresponding epoxides under mild conditions.

Graphical abstractIncorporation of a salpr schiff base ligand within the large pores of mesoporous material MCM-41 and subsequent treatment with MoO2(acac)2 affords a new truly heterogeneous molybdenum catalyst for successful epoxidation of cycooctene,cyclohexene,1-octene and 1-hehene with TBHP with high selectivities, turnover frequencies, and stability. Figure optionsDownload full-size imageDownload as PowerPoint slide