Synthesis of multi-amine functionalized hydrogel for preparation of noble metal nanoparticles: utilization as highly active and recyclable catalysts in reduction of nitroaromatics

Abstract

A new and one-pot protocol for mass-producable synthesis of the poly(ethylene oxide propylphosphonamidate) (PEOPPA) hydrogel bearing multi-amine and multi-amino groups with excellent swellability and flexibility has been described. The structural characterization of the formed gel was well analyzed by infrared, solid state 31 P-NMR and X-ray photoelectron spectroscopies, and scanning electron microscopy. Rheological properties and swellability are carefully measured and discussed as well. The PEOPPA hydrogels have been used as a template and reducing agent for the synthesis of a series of noble metal nanoparticles (MNPs) (Au, Ag, Pd, Pt and Ru NPs) in the absence of any other reducing agents and stabilizers. In situ formed MNPs were uniformly impregnated inside the hydrogel without secession, efficiently avoiding aggregation-induced loss of catalytic activity. The MNP-impregnated hydrogels were employed for the reduction of various nitroaromatics in the presence of sodium borohydride in aqueous media, showing very high catalytic activity. These systems exhibit excellent recyclability in an easy way. The catalytic activity in enhancing the conversion rate increases in accordance with a series: PEOPPA hydrogel supported (HS) Ru NP , HS Ag NP , HS Au NP , HS Pt NP , HS Pd NP. The reaction rate constants at 10, 30 and 50 uC and the activation energies with other activation parameters were estimated. The activation energies for the reduction of 2,6-dinitrophenol, 2,4-dinitrophenol, 4-nitrophenol and 2,4,6-trinitrophenol catalyzed by the HS Au NP are 35.13, 29.08, 22.03 and 32.01 kJ mol 21 , respectively.

Organic/inorganic nanocomposite hydrogels

“…These polymers contain poly(3,4-ethylenedioxythiophene) (Xiao et al, 2013), poly(ethylene oxide propylphosphonamidate) (Zhang et al, 2013), dextran (Ma et al, 2009), dialdehyde starch (Xia et al, 2012), and so on. These polymers contain poly(3,4-ethylenedioxythiophene) (Xiao et al, 2013), poly(ethylene oxide propylphosphonamidate) (Zhang et al, 2013), dextran (Ma et al, 2009), dialdehyde starch (Xia et al, 2012), and so on.…”

In situ template synthesis of gold nanoparticles using a bis-imidazolium amphiphile-based hydrogel

“…Poly(ethylene oxide propylphosphonamidate) hydrogels were reported as being able to reduce anions of some metals, obtaining the respective NPs. The metals used were gold, silver, palladium, platinum and ruthenium [18]. Amphiphilic amino acid-based gelators [19,20] and oligopeptide gelators [21] have the ability to reduce the gold ions, allowing the formation of GNPs.…”

“…The gels acts as template matrix, to control the size of the NPs, but also prevents their aggregation. The NPs included in the gel can form a composite with a defined function, for example as catalyst [18], sensor [25] or antibacterial material [15].…”

Chemoselective Reductions of Nitroaromatics in Water at Room Temperature

“…6 Most recently, MO 3 S 4 cluster catalysts have been developed that offer impressive chemoselectivity and functional group tolerance, but have limitations due to their cost and complexity. 7 Additional exotic solutions, such as the use of copper, 8a iron, 8b or precious metal 8c nanoparticles, or other engineered nanomaterials, 9 have demonstrated good activity, but may suffer from a similar lack of selectivity.…”