Rhodium Nanoparticles Stabilized by Sulfonic Acid Functionalized Metal-Organic Framework for the Selective Hydrogenation of Phenol To Cyclohexanone

Abstract

Rhodium(0) nanoparticles stabilized by sulfonic acid functionalized metal-organic framework (Rh@SMIL-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@SMIL-101 material was done by using multi pronged analyses including ICP-OES, EA, P-XRD, XPS, DR-UV-vis, BFFEM, 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 degrees C and 5 bar initial H-2 pressure). We found that Rh@S-MIL-101 catalyst selectively hydrogenated phenol to cyclohexanone with high activity (initial TOF= 78 mol cyclohexanone/mol Rh x h) and selectivity (>92%) at almost complete conversion (>95%). Moreover, the resulting rhodium nanopartides 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. (C) 2015 Elsevier B.V. All rights reserved.