Covalent organic frameworks with high quantum efficiency in sacrificial photocatalytic hydrogen evolution

Area of Science:

• Materials Science
• Photocatalysis
• Organic Semiconductors

Background:

• Organic semiconductors are tunable photocatalysts but suffer from low activity due to poor exciton dissociation.
• Efficient exciton dissociation is crucial for enhancing photocatalytic performance.

Purpose of the Study:

• To improve the photocatalytic activity of organic semiconductors.
• To prolong charge carrier lifetimes in covalent organic framework nanosheets.

Main Methods:

• Incorporation of a donor-acceptor (β-ketene-cyano) pair into covalent organic framework nanosheets.
• Photocatalytic hydrogen evolution experiments using platinum as a co-catalyst.
• Charge carrier kinetic analysis and femtosecond transient absorption spectroscopy.

Main Results:

• The modified nanosheets exhibited significantly prolonged charge carrier lifetimes.
• Apparent quantum efficiency reached up to 82.6% at 450 nm for photocatalytic H₂ evolution.
• Lower exciton binding energies were observed in the modified nanosheets.

Conclusions:

• Donor-acceptor pair incorporation effectively enhances organic photocatalyst performance.
• Prolonged charge carrier lifetimes and reduced exciton binding are key to improved activity.
• This study provides a model for understanding active species in organic photocatalysts.