Iridium Nanoparticles on SPIONs as a Catalyst for N-Heteroarene and Styrene Hydrogenation Reactions and their DFT Studies

In this study, iridium nanoparticles (IrNPs) on superparamagnetic iron oxide nanoparticles (SPIONs) are used to catalyze N-heteroarene and styrene hydrogenation processes. The IrNP@SPIONs catalyst was fabricated by reducing the Ir-salt precursors in deionized water on SPIONs (Fe₃O₄), and its catalytic reactivity for the hydrogenation of N-heteroarenes and styrene under mild reaction conditions as hydrogen under pressure was evaluated. The catalyst was characterized by FTIR, Raman, XRD, SEM, XPS, ICP-OES, and TEM. The results showed that IrNPs@SPIONs exhibited >99 % conversion with 1,2,3,4-tetrahydroquinoline (py-THQ) selectivity under 30 bar H₂ at 100 °C temperature in 24 h using DCM as a solvent. The functional group tolerance of 6-chloroquinoline demonstrated 99 % chemoselectivity towards the 6-chloro-tetrahydroquinoline (6-Cl-py-THQ) formation. The reactivity trend in 2-, 4-, and 8-methylquinoline was evaluated and corroborated with the DFT studies. The catalytic application was extended to the hydrogenation of styrene, which resulted in a 70 % conversion with >99 % ethylbenzene selectivity. The hydrogenation of 2-bromostyrene produced a 75 % conversion with >99 % chemoselectivity of 2-bromoethylbenzene.