Iterative Preparation of Platinum Nanoparticles in an Amphiphilic Polymer Matrix: Regulation of Catalytic Activity in Hydrogenation

Published as part of the Cluster Iterative Synthesis

Abstract

We demonstrate that iteration of the seeded preparation of platinum nanoparticles dispersed in an amphiphilic polystyrene–poly(ethylene glycol) resin (ARP–Pt) regulates their catalytic activity in the hydrogenation of aromatic compounds in water. The catalytic activity of the fifth generation of ARP–Pt [G5] prepared through four iterations of the seeded preparation was far superior to that of the initial ARP–Pt [G1] in the hydrogenation of aromatic compounds in water.

Key words

iterative preparation - platinum catalysis - nanoparticles - hydrogenation - aromatic compounds

• References and Notes

• 1a Aiken III JD, Finke RG. J. Mol. Catal. A: Chem. 1999; 145: 1
• 1b Astruc D, Lu F, Aranzaes JR. Angew. Chem. Int. Ed. 2005; 44: 7852
• 1c Shiju NR, Guliants VV. Appl. Catal., A 2009; 356: 1
• 1d Polshettiwar V, Varma RS. Green Chem. 2010; 12: 743
• 1e Zaera F. Chem. Soc. Rev. 2013; 42: 2746
• 2a Somorjai GA, Park JY. Top. Catal. 2008; 49: 126
• 2b Cuenya BR. Thin Solid Films 2010; 518: 3127
• 2c An K, Somorjai GA. ChemCatChem 2012; 4: 1512
• 2d Mäki-Arvela P, Murzin DY. Appl. Catal., A 2013; 451: 251

For typical examples with platinum nanoparticles, see:
• 3a Bratlie KM, Lee H, Komvopoulos K, Yang P, Somorjai GA. Nano Lett. 2007; 7: 3097
• 3b Kuhn JN, Huang W, Tsung C.-K, Zhang Y, Somorjai GA. J. Am. Chem. Soc. 2008; 130: 14026
• 3c Zhu J, Yang M.-L, Yu Y, Zhu Y.-A, Sui Z.-J, Zhou X.-G, Holmen A, Chen D. ACS Catal. 2015; 5: 6310
• 3d Bai L, Wang X, Chen Q, Ye Y, Zheng H, Guo J, Yin Y, Gao C. Angew. Chem. Int. Ed. 2016; 55: 15656
• 4a Roucoux A, Schulz J, Patin H. Chem. Rev. 2002; 102: 3757
• 4b Polavarapu L, Mourdikoudis S, Pastoriza-Santos I, Pérez-Juste J. CrystEngComm 2015; 17: 3727
• 4c Munnik P, de Jongh PE, de Jong KP. Chem. Rev. 2015; 115: 6687
• 5a Brown KR, Walter DG, Natan MJ. Chem. Mater. 2000; 12: 306
• 5b Niesz K, Grass M, Somorjai GA. Nano Lett. 2005; 5: 2238
• 5c Teranish T, Miyake M. Chem. Mater. 1998; 10: 594
• 5d Lyon JL, Fleming DA, Stone MB, Schiffer P, Williams ME. Nano Lett. 2004; 4: 719
• 5e O’Brien MN, Jones MR, Brown KA, Mirkin CA. J. Am. Chem. Soc. 2014; 136: 7603
• 6a Yamada YM. A, Arakawa T, Hocke H, Uozumi Y. Angew. Chem. Int. Ed. 2007; 46: 704
• 6b Osako T, Torii K, Uozumi Y. RSC Adv. 2015; 5: 2647
• 6c Osako T, Torii K, Tazawa A, Uozumi Y. RSC Adv. 2015; 5: 45760
• 6d Osako T, Torii K, Hirata S, Uozumi Y. ACS Catal. 2017; 7: 7371
• 7 Flow hydrogenations of C=C and C=O double bonds have been performed with ARP-Pt(G1) for up to 7852 min at 30–100 °C in aqueous medium, during which no leaching from the catalyst was observed (ICP-AES analysis). These observations showed that hydrogenation catalyzed by ARP-Pt takes place heterogeneously [see refs 6 (c) and (d)].
• 8 1 g of TentaGel S NH₂ (particle size: 90 μm) contains about 2.86 × 10⁶ beads. We estimated the densities of platinum based on the platinum loading and the volume of a polymer bead. For details, see: http://www.rapp-polymere.com/index.php?id=98.
• 9 The trans/cis ratio of 3 was about 6:4 to 7:3, suggesting that iteration of the seeded preparation did not affect the trans/cis selectivity of the fully hydrogenated product.
• 10a Uozumi Y. Bull. Chem. Soc. Jpn. 2008; 81: 1183
• 10b Uozumi Y, Tanaka K, Shibatomi K. Org. Lett. 2004; 6: 281
• 11 Iterative preparation of ARP–Pt For the initial preparation of ARP–Pt, a mixture of PS–PEG–NH₂ (TentaGel S-NH₂: 0.27 mmol/g NH₂; 3.0 g, 0.81 mmol) and K[PtCl₃(C₂H₄)]·H₂O (0.35 g, 0.89 mmol, 1.1 equiv) in H₂O (20 mL) was shaken at r.t. for 1 h under N₂. The resulting supported platinum complex was collected by filtration and washed with H₂O (3 × 20 mL). The supported platinum complex and BnOH (5 mL, 48 mmol) were added to H₂O (20 mL), and the mixture was shaken at 80 °C for 18 h. The resulting supported platinum nanoparticles were collected by filtration, washed sequentially with H₂O (3 × 20 mL) and acetone (3 × 20 mL) then dried under vacuum overnight to give black beads of the first generation of ARP–Pt (G1). For iteration of the seeded preparation, G1 was treated with K[PtCl₃(C₂H₄)]· H₂O (1.1 equiv) in H₂O (20 mL) and then reduced with BnO (5 mL) under similar conditions to the initial preparation to afford a second generation of ARP–Pt (G2). Further iterations were conducted similarly to provide G3 through G5. Hydrogenation of p-Methylstyrene (1a) in Water; Typical Procedure A Schlenk tube was charged with ARP–Pt (1 mol% Pt, 0.003 mmol) and p-methylstyrene (1a) (35.4 mg, 0.3 mmol). H₂O (3 mL) was added, and the mixture was degassed by three freeze–pump–thaw cycles. The tube was then filled with H₂ gas by using a balloon and the mixture was heated at 80 °C for 8 h. The resulting mixture was extracted with MTBE (3 × 2 mL), and the combined organic layer was analyzed by FID-GC with mesitylene as the internal standard to determine the yields of products 2a and 3a. Data for all compounds agreed well (match factor >998; structural probability >98%) with authentic GC–MS data from the NIST Reference Library; see: Stein S. E.; J. Am. Soc. Mass Spectrom. 1995, 6, 644.