Organometallic Synthesis of Bimetallic Cobalt‐Rhodium Nanoparticles in Supported Ionic Liquid Phases (Co_xRh_100−x@SILP) as Catalysts for the Selective Hydrogenation of Multifunctional Aromatic Substrates

Abstract

The synthesis, characterization, and catalytic properties of bimetallic cobalt‐rhodium nanoparticles of defined Co:Rh ratios immobilized in an imidazolium‐based supported ionic liquid phase (CoxRh100−x@SILP) are described. Following an organometallic approach, precise control of the Co:Rh ratios is accomplished. Electron microscopy and X‐ray absorption spectroscopy confirm the formation of small, well‐dispersed, and homogeneously alloyed zero‐valent bimetallic nanoparticles in all investigated materials. Benzylideneacetone and various bicyclic heteroaromatics are used as chemical probes to investigate the hydrogenation performances of the CoxRh100−x@SILP materials. The Co:Rh ratio of the nanoparticles is found to have a critical influence on observed activity and selectivity, with clear synergistic effects arising from the combination of the noble metal and its 3d congener. In particular, the ability of CoxRh100−x@SILP catalysts to hydrogenate 6‐membered aromatic rings is found to experience a remarkable sharp switch in a narrow composition range between Co25Rh75 (full ring hydrogenation) and Co30Rh70 (no ring hydrogenation).

Microenvironment engineering of supported metal nanoparticles for chemoselective hydrogenation

“…Besides small organic molecules, ionic liquid (IL) was also grafted on silicas for the stabilization of metal NPs. [56][57][58][59][60] Leitner et al demonstrated the versatility of this molecular approach for the preparation of multifunctional catalysts. 56 Moreover, polymers could also be incorporated in the nanopore of mesoporous silicas by dispersing the polymers on the mesoporous silicas or by in situ polymerization in mesoporous silicas.…”

Atomic force microscopy probing interactions and microstructures of ionic liquids at solid surfaces

“…They show many exceptionally attractive properties, such as nonflammability, excellent thermal stability, negligible vapor pressure, intrinsic ionic conductivity, molecular designability and a wide electrochemical voltage window. [1][2][3][4][5] These and other unique properties make ILs highly promising in various fields, such as lubrication, 6,7 energy storage, [8][9][10][11][12][13][14][15] gas separation, [16][17][18] and green catalysis, 19,20 to mention a few.…”

Molecular interactions of ionic liquids with SiO2 surfaces determined from colloid probe atomic force microscopy

“…Ionic liquids (ILs) are molten salts with melting points below 100 1C, showing exceptionally attractive properties for many applications, such as low vapor pressure, high chemical and thermal stability, high ionic conductivity, wide electrochemical windows, etc. [1][2][3] These unique properties make them highly promising molecular systems in many areas, including lubrication, 4,5 energy storage, [6][7][8][9] gas separation, [10][11][12][13] and green catalysts, 14,15 to mention a few.…”