Rhodium nanoparticles stabilized by sulfonic acid functionalized metal-organic framework for the selective hydrogenation of phenol to cyclohexanone

• For the first time, Rh@S-MIL-101catalyst was synthesized and characterized.
• For the firsttime, Rh@S-MIL-101 catalyst was used in phenol hydrogenation.
• Rh@S-MIL-101 provides remarkable catalytic performance in terms of activity, selectivity and reusability.

Rhodium(0) nanoparticles stabilized by sulfonic acid functionalized metal-organic framework (Rh@S-MIL-101) were prepared, for the first time, by using a direct cationic exchange approach and subsequent reduction with sodium borohydride at room temperature. The characterization of the resulting Rh@S-MIL-101 material was done by using multi pronged analyses including ICP-OES, EA, P-XRD, XPS, DR-UV–vis, BFTEM, HRTEM, STEM-EDX and N2-adsorption–desorption technique, which revealed that the formation of rhodium(0) nanoparticles (2.35 ± 0.9 nm) stabilized by the framework of S-MIL-101 by keeping the host framework intact (Rh@S-MIL-101). The catalytic performance of Rh@S-MIL-101 in terms of activity, selectivity and stability was demonstrated in the hydrogenation of phenol under mild conditions (at 50 °C and 5 bar initial H2 pressure). We found that Rh@S-MIL-101 catalyst selectively hydrogenated phenol to cyclohexanone with high activity (initial TOF = 78 mol cyclohexanone/mol Rh × h) and selectivity (>92%) at almost complete conversion (>95%). Moreover, the resulting rhodium nanoparticles were found to be highly stable against leaching and sintering, which makes Rh@S-MIL-101 reusable heterogeneous catalyst without losing of significant activity and selectivity.

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