Tungsten-Based Metal-Organic Compounds for Efficient H₂O₂ Photoproduction

Abstract

Solar power is the most promising sustainable energy in the 21st century. Solar-to-chemical energy conversion generates important industrial products such as H₂O₂, which plays vital roles in organic synthesis, wastewater treatment, medical disinfection, paper industry, etc. In case of pollutant treatment, China has employed Rural Revitalization Strategy with great effort since 2018, pursuing integrated urban-rural development, human-nature harmony and ensuring food security. Large demand will rise for wastewater treatment in mainland China. Therefore, developing advanced technology for highly efficient H₂O₂ production is of great significance.

In the past few years, there has been growing interest in H₂O₂ photoproduction. TiO₂-based materials and 2D COFs have been widely studied and developed. However, issues such as the need for sacrificial agents, oxygen pumping, UV light, and difficulties in post-reaction H₂O₂ extraction hinder the broader adoption of this technology.

MOF contains active metal center and stable crystal structure; the organic frameworks are also highly tunable for gas adsorption. French Chemist Gérard Férey largely developed MIL MOFs using a wide range of metal centers and terephthalic acid ligands. Herein, tungsten-based metal-organic catalytic system for efficient H₂O₂ photocatalysis has been preliminary developed including two major works. Firstly, MIL (W) with W center and -NH₂ substituted terephthalic acid is synthesized. The [WO₆]^6- center contains 28.64% oxygen vacancy, and H₂O₂ photoproduction rate up to 16.5 mmol·h^–1·L^–1 is achieved. A multistage solar driven evaporation system further increases H₂O₂ concentration to 0.43 wt%, reaching application level for water treatment. Secondly, MIL-OH-W, MIL-2OH-W and MIL-NO₂-W with -OH, 2 -OH, and -NO₂ substituted terephthalic acid are synthesized. MIL-2OH-W shows better crystallinity with 30% oxygen vacancy, H₂O₂ production of 20.67 mmol·L^-1, quantum efficiency reaching 36.57%, solar-to-chemical conversion efficiency up to 2.74% and turn over frequency up to 4.27 h^-1 under mild condition. The multistage solar driven evaporation system further increases H₂O₂ concentration to 1.34wt%, three times as much as the previous work. Such efficient production originates from thermal-photocatalysis coordination and ultrafast hole transfer.

In the future, the tungsten-based metal-organic catalytic system will be continuously expanded and utilized in multiple areas. Our work highlighted the potential of coordination compound based photocatalyst for scale-up and on-demand H₂O₂ production.

Date of Award	18 Sept 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Ruquan YE (Supervisor)