Cellulosic protic ionic liquids hydrogel: A green and efficient catalyst carrier for Pd nanoparticles in reduction of 4-nitrophenol in water

Abstract

The design and fabrication of functional hydrogel materials for environmental catalysis is a frontier topic both in fields of material science and catalysis. In this study, a new cellulosic hydrogel anchoring 1,1,3,3-tetramethyl guanidinium–based ionic liquids moiety (CHI) was firstly prepared by simply adding bicyclic anhydrides into newly developed 1,1,3,3-tetramethyl guanidine/DMSO/CO2 solvent system for cellulose. The presence and amount of bicyclic anhydrides as a cross linker was proved to be an important factor for the hydrogel formation. And then, Pd nanoparticles (NPs)@CHI composites were fabricated by the reduction of the absorbed Pd(II) ions on CHI using NaBH4 as reducing agent. The samples were characterized by techniques of 1H NMR, 13C NMR, FT-IR, SEM, TEM, EDX, XPS, XRD and ICP-OES analysis. It was identified that the CHI presented good immobilization capacity of Pd NPs, and the achieved Pd NPs@CHI composite had high catalytic activity and excellent reusability for the reduction of 4-nitrophenol in water. The activation parameters of the reduction reaction of 4-nitrophenol catalyzed by Pd NPs@CHI using NaBH4 were calculated as Ea = 10.8 kJ mol−1, ΔH# = 8.1 kJ mol−1 and ΔS# = −234.8 J mol−1 K−1.