Surface Charge Modulation in Covalent Organic Frameworks for Controlled Pt-Photodeposition and Enhanced...

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Covalent organic frameworks (COFs) are emerging organic photocatalysts for hydrogen evolution reaction (HER).
• While structural and optoelectronic properties are studied, the impact of surface charge on COF-based HER is less understood.
• Interfacial interactions are crucial for optimizing photocatalytic efficiency.

Purpose of the Study:

• To investigate the effect of surface charge modulation on COF photocatalysis for HER.
• To explore how altering linkage types (imine vs. amide) in thiophene-based COFs influences surface charge and catalytic performance.
• To demonstrate a novel strategy for enhancing photocatalytic HER using COFs.

Main Methods:

• Synthesis of thiophene-based COFs with imine and amide linkages.
• Zeta potential measurements to determine surface charge in the presence of ascorbic acid.
• Photoreduction of [PtCl6]2- to platinum nanoparticles (Pt NPs) as a model reaction.
• Evaluation of photocatalytic HER rates for both COF types.

Main Results:

• Amide-linked COFs exhibit negative surface charge due to lower basicity and deprotonation, while imine-linked COFs are positively charged.
• The electrostatic differences influence Pt NP formation: imine-linked COFs yield small (1-2 nm) Pt NPs, while amide-linked COFs produce larger (up to 100 nm) Pt NPs.
• Amide-linked COFs demonstrate a 300% increase in photocatalytic HER rate compared to imine-linked COFs, attributed to enhanced electron transport and Pt growth.

Conclusions:

• Surface charge modulation is a viable strategy for controlling photocatalytic processes in COFs.
• Altering COF linkage chemistry provides a pathway to tune surface charge and optimize HER performance.
• This study expands the application of COFs in photocatalysis by introducing charge-based control mechanisms.