Controllable synthesis of niobium doped mesoporous silica materials with various morphologies and its activity for oxidative catalysis

• Two dimensional hexagonal mesoporous silica (HMS-X).
• Variation of morphology with synthesis parameter.
• Small angle X-ray scattering (SAXS).
• Ethylbenzene oxidation.

Nb doped HMS-X (Nb-HMS-X) was synthesized by sol–gel/emulsion method using non-ionic tri-block copolymer surfactant PEO140PPO39PEO140 (P123) as a structure directing agent. The effect of synthesis condition on the pore morphology and nature of pore ordering was investigated. Small-angle X-ray Scattering (SAXS) revealed highly ordered pore structure in Nb-HMS-X. It is demonstrated by Field Emission Scanning Electron Microscopy (FESEM) that the materials possessed various morphologies such as, regular spheres, disordered and tube-spheres depending on synthesis conditions. The solid state 29Si nuclear magnetic resonance measurements showed that chemical environment of silicon atoms get modified significantly with synthesis condition. Furthermore, the synthesized niobium doped hollow mesoporous silica (Nb-HMS-X) was effective to catalyze ethyl benzene oxidation reaction where activation of C–H bond took place.

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