Limitation of WO₃ in Zn-Co₃O₄ Nanopolyhedra by the Pyrolysis of H₃PW₁₂O₄₀@BMZIF: Synergistic Effect of Heterostructure and Oxygen Vacancies for Enhanced Nitrogen Fixation

The photocatalytic nitrogen fixation process is a crucialsteptoward carbon neutrality and sustainable development. The combinationof polyoxometalates and metal-organic frameworks is a viablemethod to achieve high-efficiency photocatalytic nitrogen fixation.In this work, we employed bimetallic ZIF (BMZIF) composed of Co2+ and Zn2+ encapsulated with H3PW12O40 (PW12) as the precursor to synthesizeZn-doped Co3O4 nanopolyhedra loaded with WO3 nanoparticles. The NH3 yield of WO3/Zn-Co3O4-2 with the best photocatalytic performancecan reach 231.9 mu mol g(-1) h(-1) under visible light, about 2.4 and 6.4 times those of pure Zn-Co3O4 and WO3, respectively. The rhombicdodecahedral geometry of BMZIF is still maintained in the synthesizedWO(3)/Zn-Co3O4 nanopolyhedra, withthe significant increase in the specific surface area after calcinationshowing better catalytic performance. At the same time, Zn dopingand the formation of WO3 nanoparticles result in abundantoxygen vacancies in WO3/Zn-Co3O4 heterostructures.Oxygen vacancies can supply nitrogen with active sites for adsorptionand activation and improve photocarriers' capacity for separation,which can greatly increase the effectiveness of the photocatalyticsynthesis of ammonia. This work can easily synthesize the heterostructurebased on n-type WO3 nanoparticles and p-type Zn-doped Co3O4 nanopolyhedra, and the beneficial combinationof POMs and metal-organic framework provides new thinking forthe synthesis of efficient nitrogen-fixing photocatalysts. In this paper, we employed bimetallicZIF (BMZIF) composedof Co2+ and Zn2+ encapsulated with H3PW12O40 (PW12) as a precursor tosynthesize the heterostructure based on n-type WO3 nanoparticlesand p-type Zn-doped Co3O4 nanopolyhedra. Undervisible light, the NH3 production rate of WO3/Zn-Co3O4-2 with the highest photocatalyticactivity is 231.9 mu mol g(-1) h(-1). The beneficial combination of POMs and metal-organic frameworkprovides a new idea for the design of efficient nitrogen fixationphotocatalysts.