Ho-Loaded ZIF-L/COF Heterojunctions as Efficient Photocatalysts for H₂O₂ Production.

Area of Science:

• Materials Science
• Catalysis
• Photochemistry

Background:

• Covalent organic frameworks (COFs) show promise as photocatalysts for H2O2 production via oxygen reduction reaction (ORR).
• Challenges include inefficient charge separation and limited O2 activation sites, hindering catalytic efficiency.

Purpose of the Study:

• To design and synthesize a novel heterojunction material for enhanced photocatalytic H2O2 production.
• To investigate the mechanism behind the improved catalytic performance.

Main Methods:

• Fabrication of Ho-loaded ZIF-L/triazine-based COF (Ho-ZIF-L/TTA-COF) heterojunction using electrostatically induced π-π assembly.
• Characterization using in situ X-ray photoelectron spectroscopy and Kelvin probe force microscopy.
• Evaluation of photocatalytic H2O2 production under visible-light irradiation without sacrificial agents.

Main Results:

• The Ho-ZIF-L/TTA-COF heterojunction achieved a H2O2 production rate of 7.19 mmol g⁻¹ h⁻¹, a 7.6-fold increase over TTA-COF.
• Enhanced charge separation was confirmed through electron transfer from TTA-COF to ZIF-L and then to Ho species.
• Ho-ZIF-L provided exposed Ho active sites and a large surface area, facilitating efficient 2e⁻ ORR.

Conclusions:

• The Ho-ZIF-L/TTA-COF heterojunction is a highly efficient photocatalyst for H2O2 production.
• The material's design overcomes key limitations in COF-based photocatalysis.
• This work offers a promising strategy for sustainable H2O2 synthesis.