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Published May 1, 2015 | public
Journal Article Open

Heteroatom-Substituted Delaminated Zeolites as Solid Lewis Acid Catalysts


This manuscript represents a comparative study of Lewis acid catalysis using heteroatom-substituted delaminated zeolites, which are synthesized using an approach that obviates the need for surfactants and sonication during exfoliation. The comparison involves heteroatom substitution into silanol nests of delaminated zeolites consisting of DZ-1 and deboronated UCB-4. Diffuse reflectance ultraviolet (DR-UV) spectroscopy demonstrates framework heteroatom sites, and the Lewis acidity of these sites is confirmed using infrared spectroscopy of adsorbed pyridine. The enhanced catalytic accessibility of these Lewis acid sites is confirmed when performing Baeyer–Villiger oxidation of substituted 2-adamantanones with hydrogen peroxide as the oxidant. Comparison of delaminated Sn-DZ-1 with three-dimensional Sn-Beta for this reaction shows that the delaminated zeolite is more active for bulkier ketone substrates. The role of the two-dimensional crystalline framework of the delaminated zeolite on catalysis is highlighted by comparing delaminated zeolites Sn-DZ-1 with Sn-UCB-4. The former exhibits a significantly higher activity for Baeyer–Villiger oxidation, yet when comparing Ti-DZ-1 with Ti-UCB-4, it is the latter that exhibits a significantly higher activity for olefin epoxidation with organic hydrogen peroxide, whereas both delaminated zeolites are more robust and selective in epoxidation catalysis compared with amorphous Ti/SiO_2.

Additional Information

© 2015 American Chemical Society. Received: December 21, 2014; revised: March 27, 2015; published: April 1, 2015. The authors are grateful to the Management and Transfer of Hydrogen via Catalysis Program funded by Chevron Corporation. The NMR facility at Caltech was supported by the National Science Foundation under Grant No. 9724240 and supported in part by the MRSEC Program of the NSF under Award No. DMR-520565. X.O. is also grateful to Marat Orazov, Josh Pacheco, and Prof. Mark E. Davis at Caltech for providing Sn-Beta, TS-1, and other materials, as well as catalytic testing of materials for glucose-to-fructose isomerization.

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August 22, 2023
August 22, 2023