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

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/CO 2 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 NaBH 4 as reducing agent. The samples were characterized by techniques of 1 H NMR, 13 C 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 NaBH 4 were calculated as Ea = 10.8 kJ mol −1 , ΔH #  = 8.1 kJ mol −1 and ΔS #  = −234.8 J mol −1  K −1 .