Tuning excited state electronic structure and charge transport in covalent organic frameworks for enhanced photocatalytic performance

Covalent organic frameworks (COFs) represent an emerging class of organic photocatalysts. However, their complicated structures lead to indeterminacy about photocatalytic active sites and reaction mechanisms. Herein, we use reticular chemistry to construct a family of isoreticular crystalline hydrazide-based COF photocatalysts, with the optoelectronic properties and local pore characteristics of the COFs modulated using different linkers. The excited state electronic distribution and transport pathways in the COFs are probed using a host of experimental methods and theoretical calculations at a molecular level. One of our developed COFs (denoted as COF-4) exhibits a remarkable excited state electron utilization efficiency and charge transfer properties, achieving a record-high photocatalytic uranium extraction performance of similar to 6.84 mg/g/day in natural seawater among all techniques reported so far. This study brings a new understanding about the operation of COF-based photocatalysts, guiding the design of improved COF photocatalysts for many applications.

Automated summary

In this study, a family of isoreticular crystalline hydrazide-based COF photocatalysts was constructed using reticular chemistry, with their optoelectronic properties and local pore characteristics modulated by different linkers. The excited state electronic distribution and transport pathways in the COFs were investigated at a molecular level using experimental methods and theoretical calculations. One of the developed COFs, COF-4, exhibited remarkable excited state electron utilization efficiency and charge transfer properties, achieving a record-high photocatalytic uranium extraction performance of approximately 6.84 mg/g/day in natural seawater among all techniques reported so far. This study provides a new understanding of COF-based photocatalyst operation and guides the design of improved COF photocatalysts for various applications.