2D sp2 Carbon-Conjugated Covalent Organic Framework with Pyrene-Tethered TEMPO Intercalation for Photocatalytic Aerobic Oxidation of Sulfides into Sulfoxides

The 2D covalent organic frameworks (COFs) offer many 2D planes which are suitable for pi-pi stacking interactions with other conjugated molecules. To improve the photocatalytic performance of COFs, the synthesis of a pyrene-tethered 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) derivative cocatalyst is hereby described. The pyrene end of the cocatalyst is intercalated in between the layers of the 2D sp(2) carbon-conjugated porphyrin covalent organic framework (Por-sp(2)c-COF) via pi-pi stacking interactions evidenced by theoretical and experimental studies. The immobilization of pyrene-tethered TEMPO significantly enhances both the efficiency of photoinduced hole transfer and the stability of Por-sp(2)c-COF for the selective aerobic oxidation of a series of sulfides to sulfoxides under the irradiation of 623 nm red LEDs. This work highlights the merit of pi-pi stacking as a facile and efficient approach of immobilizing hole transfer cocatalysts without disrupting the physiochemical properties of the 2D COF photocatalyst.

Automated summary

This study presents a method to enhance the photocatalytic performance of COFs using π-π stacking interactions, synthesizing a pyrene-tethered TEMPO derivative cocatalyst and immobilizing it in Por-sp(2)c-COF, which significantly improves the efficiency of photoinduced hole transfer and stability for selective oxidation reactions. The research highlights the merit of π-π stacking as a facile and efficient approach for immobilizing hole transfer cocatalysts in 2D COF photocatalysts without disrupting their physiochemical properties.