Abstract
New catalysts based on Pd(0) nanoparticles (Pd NPs) on a bimodal porous silica of the UVM-7/polydopamine (PDA) support have been synthesized following two preparative strategies based on the sequential or joint incorporation of two components of the composite (Pd and PDA). We analyzed the role played by the PDA as ‘interfacial glue’ between the silica scaffold and the Pd NPs. The catalysts were tested for the hydrogenation of 4-nitrophenol using (NEt4)BH4 as the hydrogenating agent. In addition to the palladium content, the characterization of the catalysts at the micro and nanoscale has highlighted the importance of different parameters, such as the size and dispersion of the Pd NPs, as well as their accessibility to the substrate (greater or lesser depending on their entrapment level in the PDA) on the catalytic efficiency. Staged sequential synthesis has led to better catalytic results. The most active Pd(0) centers seem to be Pd NPs of less than 1 nm on the PDA surface. The efficiency of the catalysts obtained is superior to that of similar materials without PDA. A comprehensive comparison has been made with other catalysts based on Pd NPs in a wide variety of supports. The TOF values achieved are among the best described in the literature.
Highlights
The immobilization of metal nanoparticles (NPs) on inorganic, organic, or hybrid supports has attracted a considerable attention by their potential applications as efficient catalysts as it adds the classic advantages of the heterogeneous catalysis to the bottom-up approach of NP system [1]
We have studied the activity of a catalyst Pd NPs-UVM-7 consisting of Pd NPs supported on silica UVM-7 [1]
Three catalysts have been prepared through this Pathway a: Pd NPs-UVM-7/PDA-n (n = 1, 2, and 3)
Summary
The immobilization of metal nanoparticles (NPs) on inorganic, organic, or hybrid supports has attracted a considerable attention by their potential applications as efficient catalysts as it adds the classic advantages of the heterogeneous catalysis to the bottom-up approach of NP system [1]. The adhesive property of PDA on any surface together with the ability of PDA to drive the interfacial assembly of metal NPs stabilizing them and avoiding the reduction of their activity, represents a new approach in the synthesis of effective metal NPs supported catalysts. Following this approach some metal NPs-PDA-supported catalysts have been synthesized and efficiently tested in reduction of nitroarenes, oxidation of alcohols, and Susuky–Miyaura cross-coupling reactions (NPs of Pt, Pd, Ag, and Au, and SBA-15, hallosyte nanotubes, Fe3 O4 , carbon nanotubes, graphene, graphene oxide, MoS2 , and Au as supports) [2,9,10,11,12,13,14,15,16,17,18].
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