Reversing Titanium Oligomer Formation towards High-Efficiency and Green Synthesis of Titanium-Containing Molecular Sieves

Green and efficient synthesis of titanium-containing molecular sieves is limited by the quantity of environmentally unfriendly additives and complicated synthesis procedures required. Oligomerization of Ti monomers into anatase TiO2 is the typical outcome of such procedures because of a mismatch between hydrolysis rates of Si and Ti precursors. We report a simple and generic additive-free route for the synthesis of Ti-containing molecular sieves (MFI, MEL, and BEA). This approach successfully reverses the formation of Ti oligomers to match hydrolysis rates of Ti and Si species with the assistance of hydroxyl free radicals generated in situ from ultraviolet irradiation. Moreover, fantastic catalytic performance for propene epoxidation with H-2 and O-2 was observed. Compared with the conventional hydrothermal method, this approach opens up new opportunities for high-efficiency, environmentally benign, and facile production of pure titanium-containing molecular sieves.

Automated summary

The green and efficient synthesis of titanium-containing molecular sieves is hindered by environmentally unfriendly additives and complicated procedures. A new additive-free route has been developed using hydroxyl free radicals generated from ultraviolet irradiation, successfully reversing the formation of titanium oligomers to match hydrolysis rates of titanium and silicon species. This approach shows fantastic catalytic performance for propene epoxidation with H-2 and O-2, opening up new opportunities for high-efficiency, environmentally friendly, and facile production of pure titanium-containing molecular sieves compared to conventional hydrothermal methods.