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ArticleSize-Controlled Synthesis of Rhodium Nanocatalysts and Applications in Low-Temperature HydroformylationAndrew Lamkins 1,2, Charles J. Ward 1,2, Jeffrey T. Miller 3, Ziad Alsudairy 4, Xinle Li 4, Joseph Thuma 1,2, Ruoyu Cui 1,2, Xun Wu 1,2, Levi M. Stanley 1 and Wenyu Huang 1,2,*1 Department of Chemistry, Iowa State University, Ames, IA 50010, USA2 Ames Laboratory, U.S. Department of Energy, Ames, IA 50010, USA3 Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA4 Department of Chemistry, Clark Atlanta University, Atlanta, GA 30314, USA* Correspondence: whuang@iastate.eduReceived: 3 December 2024; Revised: 30 December 2024; Accepted: 3 January 2025; Published: 10 January 2025 Abstract: Controlling the size and distribution of metal nanoparticles is one of the simplest methods of tuning the catalytic properties of a material. For a nanocrystal particle, the ratio of edge-to-terrace sites can be critical in determining its catalytic activity and selectivity to desired products. To study these effects, we have developed a simple impregnation method of controlling the dispersion of rhodium atoms at the same metal loading in the range of nanoparticles less than 10 nm. Rh precursor salts are loaded onto inert SBA-15, and increasing the ratio of chloride to acetylacetonate salts improves the dispersion of rhodium atoms to form small Rh nanoparticles. Extensive characterization of the size-controlled catalysts, including XAS and in-situ CO-DRIFTS studies, has been performed to characterize the structure of Rh nanoparticles. Applying these catalysts to the hydroformylation of styrene, we observed that turnover frequency increases with decreasing particle size from 6.4 to 1.6 nm. When applied to hydroformylation reactions, we achieved a high branched product selectivity and successfully demonstrated a route to synthesizing the pain relief drug ibuprofen. This simple method can also synthesize Pt and Pd nanoparticles between 2–10 nm. 

Abstract Carbon–carbon bond cleavage reactions, adapted to deconstruct aliphatic hydrocarbon polymers and recover the intrinsic energy and carbon value in plastic waste, have typically been catalysed by metal nanoparticles or air-sensitive organometallics. Metal oxides that serve as supports for these catalysts are typically considered to be inert. Here we show that Earth-abundant, non-reducible zirconia catalyses the hydrogenolysis of polyolefins with activity rivalling that of precious metal nanoparticles. To harness this unusual reactivity, our catalytic architecture localizes ultrasmall amorphous zirconia nanoparticles between two fused platelets of mesoporous silica. Macromolecules translocate from bulk through radial mesopores to the highly active zirconia particles, where the chains undergo selective hydrogenolytic cleavage into a narrow, C 18 -centred distribution. Calculations indicated that C–H bond heterolysis across a Zr–O bond of a Zr(O) 2 adatom model for unsaturated surface sites gives a zirconium hydrocarbyl, which cleaves a C–C bond via β-alkyl elimination.