Abnormal Multistep Charge Transfer in a 2D Single-Crystalline Covalent Organic Framework Photocatalyst

Area of Science:

• Materials Science
• Photocatalysis
• Renewable Energy

Background:

• Artificial photosynthesis aims to mimic natural processes for energy conversion.
• Multielectron redox reactions are crucial but challenging to replicate artificially.
• Covalent organic frameworks (COFs) offer tunable structures for catalytic applications.

Purpose of the Study:

• To investigate charge transfer mechanisms in a novel two-dimensional single-crystalline COF.
• To explore the potential of this COF for efficient carbon dioxide photoreduction.
• To understand the structure-property relationships governing photocatalytic activity.

Main Methods:

• Continuous rotation electron diffraction for crystal structure determination.
• Theoretical simulations for mechanistic insights.
• Photocatalytic experiments for CO2 reduction and product analysis.

Main Results:

• A single-crystalline COF, USTB-35-Cu, with staggered porphyrin-perylenediimide layers was synthesized.
• Abnormal multistep charge transfer was observed, involving sequential electron transfer and proton-coupled electron transfer.
• High methane production rate (188 μmol g⁻¹ h⁻¹) and selectivity (99%) for CO2 photoreduction were achieved.

Conclusions:

• Single-crystalline COFs can effectively couple multistep charge transfer with multielectron CO2 photoreduction.
• The discovered mechanism provides a new pathway for designing advanced photocatalysts.
• This work advances the field of artificial photosynthesis and sustainable energy solutions.