Hybrid mesoporous materials with a uniform ligand distribution: Synthesis, characterization, and application in epoxidation catalysis

A novel mesoporous MCM-41-type of hybrid material was synthesized by co-condensation of tetraethyl orthosilicate and the chelate ligand (3-trimethoxysilylpropyl)[3-(2-pyridyl)-1-pyrazolyl]acetamide (1) in the presence of cetyltrimethylammonium bromide as template. Surfactant extraction produced hybrid mesoporous materials with uniform mesoscale channels, large pore volumes, and high specific surface areas. The preservation of the chelate ligand structure during the hydrothermal synthesis and the acid extraction process was confirmed by C-13 CP-MAS NMR spectroscopy. Solid epoxidation catalysts can be obtained by introducing oxodiperoxomolybdenum species MOO(O-2)(2) into the hybrid materials via a ligand exchange reaction. All molybdenum-containing catalysts showed high activity for the liquid-phase epoxidation of cyclooctene with (BuOOH)-Bu-t and stability against leaching of active molybdenum species. The excellent stability of these catalysts indicated that almost all the incorporated chelate ligands are chemically accessible for the coordination of the catalytically active MOO(O-2)(2) moieties.