Process coupling of CO₂ reduction and 5-HMF oxidation mediated by defect-enriched layered double hydroxides

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Developing sustainable methods for waste carbon utilization is crucial.
• Layered double hydroxides (LDHs) offer potential as catalytic materials.
• 5-hydroxymethylfurfural (5-HMF) is a key platform chemical derived from biomass.

Purpose of the Study:

• To develop a photocatalytic coupling process for CO2 reduction and 5-HMF oxidation.
• To investigate the role of metal vacancies in layered double hydroxides for enhanced catalysis.
• To understand the mechanism of defect-induced performance enhancement in LDHs.

Main Methods:

• Synthesis of ZnNiFe-LDH via co-precipitation.
• Selective etching of Zn2+ ions to introduce metal vacancies.
• Characterization using ICP-AES, EPR, and XPS.
• Photocatalytic experiments under UV-vis irradiation.
• Isotope labeling (13CO2) and in situ FTIR for mechanistic studies.

Main Results:

• CO2 was effectively stored as carbonate within the LDH structure.
• Etching introduced controllable Zn vacancies, optimizing the electronic structure of LDH nanosheets.
• Photocatalytic coupling of CO2 reduction to CO and 5-HMF oxidation to DFF was achieved.
• LDHs etched for 3 hours showed a 2.84-fold increase in CO yield and a 2.82-fold increase in DFF yield compared to unetched LDHs.
• The study elucidated the coupling mechanism and the role of defects in enhancing catalytic activity.

Conclusions:

• Defect engineering in LDHs is an effective strategy to enhance photocatalytic performance.
• The developed process offers a promising route for the comprehensive utilization of carbon resources.
• The findings contribute to the advancement of sustainable chemical synthesis and catalysis.