Boosting Dodecahydro- <i>N</i> -ethylcarbazole Dehydrogenation Efficiency on Pt/ <i>n</i> %TiO ₂ @MCM-41 via Enhanced C–H Activation by Strengthening Metal–Support Interaction

Dodecahydro-N-ethylcarbazole (12H-NEC), a promising hydrogen carrier, faces problems, like low dehydrogenation activity and selectivity, which hinder its practical application. Pt/n%TiO2@MCM-41 (n = 8–24) were prepared in this work to boost the dehydrogenation performance of 12H-NEC. In such a catalyst, Pt nanoparticles (NPs) were anchored on n%TiO2@MCM-41. The composite, n%TiO2@MCM-41, was synthesized by the hydrolysis of tetraethyl orthotitanate onto MCM-41. Subsequently, changes in the structure and dehydrogenation activity after the introduction of TiO2 were investigated. Characterization results, such as electron paramagnetic resonance spectra and high-resolution transmission electron microscopy images, showed the presence of the Si–O–Ti interface, abundant oxygen vacancies, and electron-rich Pt NPs in Pt/n%TiO2@MCM-41. Among the evaluated catalysts, the dehydrogenation activity increased with the loading amount of TiO2, and Pt/24%TiO2@MCM-41 exhibited the optimum catalytic activity. The rate-limiting step, 4H-NEC dehydrogenation, was facilitated by the introduction of TiO2. Compared to Pt/TiO2, Pt/n%TiO2@MCM-41 catalyzed the reaction with reduced side reactions, owing to its lower total acid content. Furthermore, theoretical calculation results showed that Pt5/TiO2@MCM-41 promoted the cleavage of the C–H bond more effectively than Pt5/TiO2 did, thereby improving the dehydrogenation of 12H-NEC.