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

摘要

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.

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