Covalent organic frameworks (COFs) are a class of porous materials that have shown great promise in solar energy conversion. However, understanding of the correlation between their structure, photophysics, and photocatalytic properties remains sparse. We report a significant step towards filling this knowledge gap by studying twin COFs with reversed imine connectivity, revealing that imine-linkage imparts directionality to intramolecular charge transfer (ICT) – which we term an “ICT Tesla Valve”. This reversal affects uptake of Re molecular catalyst (MC) and leads to a slowdown in the light driven CO2→CO reduction. We rationalize this effect by considering Re-f-COF, with ICT in the forward direction, functions as an efficient CO2 photoreduction catalyst but Re-r-COF, with ICT in the reverse direction, struggles to perform the same CO2 photoreduction. The effect of ICT towards/away from MC in Re-f-COF and Re-r-COF, respectively, leads to a key difference in the electron transfer which is enabled by forward ICT in Re-f-COF but inhibited by reverse ICT in Re-r-COF. These findings are unprecedent, revealing not only that the linker chemistry should be recognized as a key factor to consider in the development of COF photocatalysts but also provides a unique approach to tailor photocatalysts capable of performing both reduction and oxidation half reactions for complete artificial photosynthesis.

Exercising control over CO2 photoreduction through imine reversal in covalent organic frameworks

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.