Visible-Light-Responsive UiO-66(Zr) with Defects Efficiently Promoting Photocatalytic CO₂ Reduction

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Understanding atomic-level structure-property relationships is crucial for designing efficient heterogeneous catalysts.
• Elucidating the role of specific active site structures in catalytic activity remains a challenge.
• Metal-organic frameworks (MOFs) offer tunable structures for catalytic applications.

Purpose of the Study:

• To synthesize MOF catalysts with all-solid-state frustrated Lewis pairs (FLPs) using UiO-66(Zr) as a prototype.
• To investigate the photocatalytic activity of defect-engineered UiO-66(Zr) for CO2 reduction under visible light.
• To elucidate the mechanism of CO2 activation by FLPs at the atomic level.

Main Methods:

• In situ synthesis of MOF catalysts (UiO-66(Zr)) using acetic acid as a modulator.
• Introduction of missing linkers to create defects and visible-light responsiveness.
• In situ Fourier transform infrared (FTIR) spectroscopy to identify reaction intermediates.

Main Results:

• UiO-66(Zr) with introduced defects exhibited visible-light-responsive photocatalytic activity for CO2 reduction.
• All-solid-state frustrated Lewis pairs (FLPs) of Zr3+-OH were successfully synthesized in situ.
• The intermediate b-CO3^2- was identified as key for CO2 activation by Zr3+-OH FLPs.
• Defective UiO-66(Zr) demonstrated a "self-breathing" behavior attributed to surface hydroxyls.

Conclusions:

• Defect engineering provides a novel strategy to utilize UV-responsive MOFs, enhancing their photocatalytic capabilities.
• The study elucidates the atomic-level mechanism of CO2 activation by FLPs in MOFs.
• This work opens new avenues for designing advanced MOF-based catalysts for CO2 conversion.