A novel magnetic cluster modified palladium-cellulose nanocrystal hybrids as recyclable catalyst for 4-nitrophenol reduction. (December 2022)

• Record Type: Journal Article
• Authors: Xu, Jiaxin; Wang, Yi; Zhao, Weinan; Han, Lian; Tam, Kam Chiu
• Is Part Of: Materials today communications. Volume 33(2022)
• Publication Date: 2022-12
• Subjects: Nanogel -- Emulsion polymerization -- Magnetic particles (MNPs) -- Palladium catalyst -- 4-NP reduction -- Melamine formaldehyde -- Polydopamine; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2022.104349
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: The development of noble metal catalysts with high catalytic performance and low metal loading has attracted much interest. However, the separation of the used nanoscale catalyst from the process is challenging. Most of the separation system, such as resin or membrane leads to a sacrifice of high surface area as well as catalytic efficiency. Herein, two series of recyclable catalysts were synthesized by loading palladium (Pd) particles onto melamine formaldehyde (MF) modified cellulose nanocrystals (CNC) and dopamine (DA) coated CNC. In situ co-precipitation of magnetic nanoparticle (MNP) clusters were used to impart magnetic characteristic to the catalysts. This magnetic cluster successfully achieved high magnetization without aggregation. The amount of palladium precursor added to the catalytic systems was optimized, where 10-Pd-PDC yielded 10.83 ± 2.43 nm discrete Pd loaded hybrids. The catalytic performance was assessed by the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydrides (NaBH4 ). The 4-NP reduction mechanisms were analyzed using the Langmuir-Hinshelwood model and the apparent rate constant k (s −1 ), turnover frequency (TOF, h −1 ) and activity factors (s −1 g −1 ) were determined to be 2.142 × 10 −3, 305.82 and 535.5 using MNP2-Pd-MC respectively. An induction time was observed for MNP4 or 5-Pd-PDC, which was attributed to the unignitable diffusion time for reagents to cross the thick PDA and MNP layer. The separation efficiency of the magnetic catalysts was evaluated by monitoring the absorbance at 400 nm as a function of separation time, and the MNP2-Pd-MC could be recycled 7 times without severe loss. Pd-MF-CNC displayed excellent catalytic performance for the reduction of 4-NP, while Pd-PDA-CNC possessed an inferior catalytic reactivity due to the reduced catalytic surface area. The developed templated MNP could be extended to other systems allowing for the recycling and reuse of the catalysts. Graphical Abstract: ga1