Pickering High Internal Phase Emulsions Templated CoOx-HPC Loading Bimetallic AuPd Nanoparticles for Catalytic Oxidation of 5-Hydroxymethylfurfural to 2, 5-Furan Dicarboxylic

The supported bimetallic AuPd nanoparticles hold great promise for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2, 5-furan dicarboxylic acid (FDCA), a substitute for petroleum derivative terephthalic acid (TPA). Herein, by combining a versatile Pickering high internal phase emulsions (HIPEs) template with subsequent carbonization process, cobalt-based hierarchical porous carbon (CoOx-HPC) support was obtained. After loading bimetallic AuPd nanoparticles through the sol-gel method, AuPd/CoOx-HPC catalyst was successfully synthesized. By changing the Pickering HIPEs parameters, carbonization temperature, the porous structure and cobalt valence of as-synthesized catalyst can be adjusted. The obtained catalysts were systematically characterized by SEM, TEM, N-2 adsorption-desorption, XRD, XPS, and TGA. Benefiting from the synergistic effects of the high porosity of CoOx-HPC support and efficient AuPd nanoparticles, tandem oxidation of HMF to FDCA can be carried out in the water. We have clarified that the catalysts with various cobalt valence states showed superior performance, and the highest FDCA yield of 97.2 % will be obtained under the optimal reaction conditions. Meanwhile, the kinetics study indicated that the oxidation of FFCA to FDCA was the rate-determining step. Moreover, the AuPd/CoOx-HPC catalyst revealed excellent stability in HMF oxidation during four cycles. The experimental results demonstrated that as-prepared AuPd/CoOx-HPC catalysts are efficient towards FDCA production from the selective oxidation of HMF.