A one-step rapid synthesis of TS-1 zeolites with highly catalytically active mononuclear TiO₆species

The modulation and determination of the coordination environments of Ti active sites in titanosilicate zeolites are key challenges in the rational design of high-performance heterogeneous catalysts. Up to now, the highly catalytic active Ti species, while not yet unambiguously determined, is mainly constructed by the complex post-treatment method, in which it is difficult to precisely control the distribution of the created Ti species. Herein, we showcase a facile strategy for the one-step rapid synthesis of TS-1 (MFIframework type) zeolites with highly catalytically active Ti speciesviaactive seed-assisted microwave irradiation. The coordination environment and local structure of the Ti species in TS-1 zeolites were investigatedviaUV-vis, UV-Raman, and X-ray absorption spectroscopies. Significantly, according to the elaborate characterizations based on the extended X-ray absorption fine structure (EXAFS), these highly catalytically active Ti species were clearly identified as novel mononuclear TiO₆species. Experimental studies revealed that the active seeds can provide plenty of high-coordinated Ti precursors, which play a critical role in creating mononuclear TiO₆in the zeolite framework coupled with microwave irradiation. Moreover, such mononuclear TiO₆species remain stable upon calcination. The obtained catalyst affords a high turnover number value (272) in the 1-hexene epoxidation reaction, which is almost 70% higher than that of the conventional TS-1 zeolite (161). This study may open new perspectives for the designed synthesis and applications of titanosilicate zeolite catalysts in various important selective oxidation reactions.