Strong Metal–Support Interaction in Rh/TiO2 Catalysts for Reductive Deuteration of Quinoline

Reductive deuteration of N-heterocycles provides an efficient route to deuterated scaffolds, yet achieving controlled deuterium incorporation in quinoline remains challenging. Herein, we report a high-temperature H2-treated Rh/TiO2 catalyst (Rh/TiO2–H500) that enables efficient reductive deuteration of quinoline using D2O as a deuterium source. Structural characterization reveals that reduction at 500 °C induces a pronounced strong metal–support interaction (SMSI), leading to partial TiOx encapsulation of Rh nanoparticles and interfacial electron transfer that generates electron-rich Rh0 species. This optimized interfacial structure promotes cooperative C–H activation and effective H/D transfer across the reduced quinoline framework, affording high deuterium incorporation at multiple positions of 1,2,3,4-tetrahydroquinoline (THQ). These results highlight the importance of SMSI-driven electronic and interfacial modulation in regulating reductive H/D exchange over heterogeneous catalysts.