Mn-Schiff base modified MCM-41, SBA-15 and CMK-3 NMs as single-site heterogeneous catalysts: Alkene epoxidation with H2O2 incorporation

• Mn-catalysts were synthesized by covalent grafting onto SBA-15, MCM-41 and CMK-3.
• These catalysts are effective and selective towards epoxides with H2O2 and CH3COONH4.
• MnII-L@CMK-3 provides high TONs and is kinetically very fast demonstrating extremely high TOFs.

The development of new functional catalytic materials prepared via appropriate chemical modification of mesoporous silica SBA-15, MCM-41 or carbon nanomaterials CMK-3, are presented. Their synthesis has been carried out via two synthetic approaches: (a) a two steps procedure which includes grafting of the Schiff base ligand 1,3-bis[3-aza-3-(1-methyl-3-oxobut-1-enyl)-prop-3-en-1-yl]-2-(4-hydroxy-phenyl)-1,3-imidazolidine (L) onto the suppors and subsequent metalation of the so-formed hybrid material, and (b) an one step procedure which allows covalent grafting of the entire [MnII-Schiff base] catalyst onto the carbonaceous support. The resulting single-site heterogeneous catalysts were characterized and evaluated for alkene epoxidation with H2O2 in the presence of CH3COONH4 as additive. They are efficient and selective towards formation of epoxides. The highest TONs have been achieved by L@MCM-41-MnII and MnII-L@CMK-3. Moreover, MnII-L@CMK-3 is operative for a second use and kinetically very fast, demonstrating remarkably high TOFs 65–634 h−1 that is correlated to its practically zero porosity. Based on the present data, the textural features of the obtained catalysts are discussed in correlation with their catalytic performance.

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