Selective Catalytic Chemistry at Rhodium(II) Nodes in Bimetallic Metal-Organic Frameworks

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) offer tunable structures for catalysis.
• Highly dispersed metal sites within MOFs are potential catalytic centers.
• Previous studies have not explored MOF metal nodes as gas-phase reaction catalysts.

Purpose of the Study:

• To investigate the catalytic activity of metal nodes in MOFs for gas-phase hydrogenation.
• To identify and characterize the active sites responsible for catalysis in a CuRhBTC MOF.
• To elucidate the mechanism of propylene hydrogenation catalyzed by MOF-based sites.

Main Methods:

• Synthesis and characterization of CuRhBTC metal-organic framework.
• Gas-phase catalytic hydrogenation of propylene.
• Multi-technique characterization including X-ray diffraction and spectroscopy.
• Density functional theory (DFT) calculations for mechanistic insights.

Main Results:

• CuRhBTC exhibited catalytic activity for propylene hydrogenation, unlike other MOFs.
• Rh in the +2 oxidation state (Rh2+) was identified at the metal nodes, a novel observation in crystalline MOFs.
• The MOF structure stabilized the active Rh2+ sites under reaction conditions.
• DFT calculations proposed a mechanism involving hydrogen dissociation and propylene adsorption at Rh2+ sites.

Conclusions:

• The study demonstrates the first instance of a gas-phase reaction catalyzed by highly dispersed sites at MOF metal nodes.
• The unique Rh2+ sites in CuRhBTC are effective for propylene hydrogenation at room temperature.
• MOFs provide a platform for rational catalyst design with controlled active site geometry and size.
• This work opens new avenues for developing advanced MOF-based catalysts for chemical transformations.