Gold-decorated polymeric monoliths: In-situ vs ex-situ immobilization strategies and flow through catalytic applications towards nitrophenols reduction

• Published in: Polymer (Guilford) 2015-10, Vol.77, p.218-226
• Main Authors: Khalil, Ahmed M., Georgiadou, Violetta, Guerrouache, Mohamed, Mahouche-Chergui, Samia, Dendrinou-Samara, Catherine, Chehimi, Mohamed M., Carbonnier, Benjamin
• Format: Article
• Language: English
• Subjects: Catalytic reduction; Ethylene; Gold; Immobilization; In-situ synthesis; Monolithic support; Nanoparticles; Nitroarenes; Nitrophenol; Permeability; Porosity; Reduction; Supported gold nanoparticles
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2015.09.040

Monolithic polymers with micrometer-sized channel-like pores and primary amine as chelating surface functionality were prepared via a two-step synthetic route. UV-induced free radical polymerization of N-acryloxysuccinimide (NAS) and ethylene dimethacrylate (EDMA) yielded to nucleophilic sensitive monolith. Subsequent surface grafting of ethylene diamine through displacement of the N-hydroxysuccinimide (NHS) leaving groups provided pores with dual hydrophilic and chelating surface properties. Amino-containing monolith was used as versatile platform for supporting gold nanoparticles (GNPs) through complexation of either preformed Au0 nanoparticles or Au3+ precursor salt followed by in situ reduction. All synthesis and surface functionalization steps were performed within micro-columns and were confirmed to occur to a large extent using a combination of experimental methods such as in-situ micro-Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis and pressure permeability tests providing information on morphology, porosity, flow-through properties and surface distribution of gold nanoparticles. Continuous flow catalytic activity of the nanostructured monolithic columns towards hydride-mediated reduction of nitrophenol isomers, namely 2-nitrophenol, 3-nitrophenol and 4-nitrophenol, and 4-nitroaniline was postulated on the basis of UV–vis spectroscopy characterization suggesting presence of the corresponding amino-derivatives. This study conclusively shows that the in-situ strategy for the surface immobilization of gold nanoparticles enables high reaction yield while maintaining unaffected the monolithic column permeability. [Display omitted] •Monolithic micro-reactors with surface immobilized gold nanoparticles for flow through catalytic processes.•Porous polymer with protonated amino surface groups as supports for gold nanoparticles.•Surface adsorption of gold nanoparticles through in-situ and ex-situ strategies.