Highly Ordered Conductive Metal-Organic Frameworks with Chemically Confined Polyoxometalate Clusters: A Dual-Functional Electrocatalyst for Efficient H₂O₂ Synthesis and Biomass Valorization.

Abstract

The design of bifunctional and high-performance electrocatalysts that can be used as both cathodes and anodes for the two-electron oxygen reduction reaction (2e^- ORR) and biomass valorization is attracting increasing attention. Herein, a conserved ligand replacement strategy is developed for the synthesis of highly ordered conductive metal-organic frameworks (Ni-HITP, HITP = 2, 3, 6, 7, 10, 11-hexaiminotriphenylene) with chemically confined phosphotungstic acid (PW₁₂) nanoclusters in the nanopores. The newly formed Ni-O-W bonds in the resultant Ni-HITP/PW₁₂ electrocatalysts modulate the electronic structures of both Ni and W sites, which are favorable for cathodic 2e^- ORR to H₂O₂ production and anodic 5-hydroxymethylfurfural oxidation reaction (HMFOR) to 2, 5-furandicarboxylic acid (FDCA), respectively. In combination with the deliberately retained conductive frameworks and ordered pores, the dual-functional Ni-HITP/PW₁₂ composites enable a H₂O₂ production rate of 9.51 mol g_cat ^-1 h^-1 and an FDCA yield of 96.8% at a current density of 100 mA cm^-2/cell voltage of 1.38 V in an integrated 2e^- ORR/HMFOR system, significantly improved than the traditional 2e^- ORR/oxygen evolution reaction system. This work has provided new insights into the rational design of advanced electrocatalysts and electrocatalytic systems for the green synthesis of valuable chemicals.