High-dispersed MoO3 nanoparticles in 3D-dendritic mesoporous silica nanospheres: heterogeneous catalysts for the epoxidation of olefins

Highly dispersed molybdenum trioxide were loaded in three-dimensional dendritic mesoporous silica nanospheres (MoO3@3D-DMSNs) by one-pot method. The mesoporous silica nanospheres with central radical channels were obtained through the interaction of bisurfactant and molybdenum source and the as-synthesized MoO3@3D-DMSNs were characterized by specific tests. As a result, the as-prepared MoO3@3D-DMSNs exhibited better catalytic performance for epoxidation of olefins. When the molar ratio value of Mo and Si is 5%, the specific surface area (SBET = 185.8 m2/g) and pore volume (Vp = 0.46 cm3/g) of MoO3@3D-DMSNs reach a maximum, and the catalytic activity is the best for the epoxidation of cyclooctene. The conversion could reach 84% with a selectivity above 98% after 6 h. The better catalytic performance can be maintained after five reaction-regeneration cycles. The dendritic mesoporous structure can be well preserved after recycling. Additionally, olefins with electron-absorbing group exhibit better catalytic activity with MoO3@3D-DMSNs-5 as catalyst. Hence, MoO3@3D-DMSNs catalysts with the center-radial oriented channel exhibit good activity and stability. The central radial channel can effectively disperse the active center MoO3 and play a key role in the transmission and accessibility of substrates, and it would have a good application prospect in the catalytic reactions.