Thiol-functionalized chitosan poly(protic ionic liquids) hydrogel selectively anchors gold nanoparticles for aqueous catalysis

Well-dispersed gold nanoparticles (Au NPs) anchored by polymeric three-dimensional hydrogels for catalysis have received great attention, especially in aqueous-phase catalysis. In this study, thiol-functionalized chitosan poly(protic ionic liquids) hydrogel (TCPPILH) is delicately designed and prepared as a selective support material to anchor Au NPs by taking advantages of Au-thiol chemistry and facile preparation of protic ionic liquids (PILs). The TCPPILH was successfully synthesized by a protonation reaction of chitosan with 3-mercaptopropionic acid (MPA) and mercaptosuccinic acid (MSA) in water, and followed by shaping in ethanol coagulation bath via solution-gelation transition, and the properties can be facilely adjusted by changing the feed ratio of MPA and MSA. It is found that the TCPPILH can act as a selective support for adsorption of Au 3+ ions, and a maximal anchoring capacity for Au NPs could reach up to 151.5 mg/g. The as-prepared TCPPILH @ Au NPs catalysts were systematically characterized by FTIR, XPS, SEM, TEM, XRD and ICP-OES analysis, and the findings demonstrated that the TCPPILH could effectively inhibit the agglomeration of Au NPs (ca. 4.20 nm in diameter). As a proof of concept, hydrogenation of water pollutes, such as 4-nitrophenol and azo dyes with NaBH 4 as reductant was selected as model applications, and the results indicated that TCPPILH @ Au NPs catalysts exhibited high catalytic activity and satisfactory reusability. Graphical abstract Thiol-functionalized chitosan poly(protic ionic liquids) hydrogel (TCPPILH) was delicately designed and prepared as a selective support material to adsorb Au 3+ and anchoring Au NPs by taking advantages of Au-thiol chemistry and facile preparation of protic ionic liquids (PILs). This TCPPILH@Au NPs catalysts exhibited desired catalytic activity for the hydrogenation of 4-nitrophenol and azo dyes in water.