Novel zirconium containing cage type silicate (Zr-KIT-5): An efficient Friedel–Crafts alkylation catalyst

• New type of Zr-incorporated cage type Fm3m silicates, Zr-KIT-5, synthesized.
• Zr incorporation as Zr4+ evident from both UV–Vis and XPS results.
• Zr-KIT-5 materials exhibit dominant Lewis acidity that increases with Zr content.
• Zr-KIT-5 highly active and stable for anisole benzylation with benzyl alcohol.

Zirconium was successfully incorporated into cubic KIT-5 mesoporous silicate by direct hydrothermal synthesis employing F127 triblock copolymer as the structure-directing agent. The Zr-KIT-5 materials exhibit relatively high specific surface area (∼1000 m2/g) and pore volumes (0.7–0.8 cm3/g), with an average cage diameter of approximately 8.8 nm as evidenced from N2 sorption and HR-TEM results. Diffuse reflectance UV–Vis spectroscopy and XPS studies reveal framework Zr4+ species that result in the formation of predominantly Lewis acid sites and some Brønsted acid sites, both of which increase with Zr content. The Zr-KIT-5 materials are shown to be highly active and stable catalysts for anisole benzylation with benzyl alcohol (BzOH) forming monobenzylated products (mainly ortho- and para-). It is shown that the benzylation activity depends mainly on the number and nature of the acid sites. Zr-KIT-5 material is thus a promising and environmentally benign Friedel–Crafts alkylation catalyst with many potential applications.

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