Natural Sunlight Photocatalytic Synthesis of Benzoxazole-Bridged Covalent Organic Framework for Photocatalysis

Abstract

Although natural sunlight-mediated photocatalysis is a clean, efficient, and green approach to access organic products, its application in the synthesis of covalent organic frameworks (COFs), however, is still unprecedented. Herein, we first report the sunlight photocatalytic synthesis of COF under ambient conditions. Furthermore, this “window ledge” reaction generated benzoxazole-linked COF is stable and can be applied as a reusable photocatalyst to highly promote visible-light-driven aerobic oxidation of sulfides to sulfoxides. These results not only enrich the COF synthetic methodology but also open a new route to access COFs in a green and sustainable way.

The tail of imidazole regulated the assembly of two robust sandwich-type polyoxotungstate-based open frameworks with efficient visible-white-light-driven catalytic oxidation of sulfides

“…Indeed, LCU-20 exhibited superior photocatalytic activities under white LED light conditions for selective oxidation of sulfides than those of the reported results under blue LED light. 15,17…”

“…9,10 Photocatalytic oxidation of sulfides features the advantages of simple operation, mild reaction conditions, low cost, and environmental friendliness, providing an alternative strategy. 11–14 Until now, various photocatalysts including organic materials 15 and metal complexes 16 have been investigated for the aerobic oxidation of sulfides and have made tremendous progress. For instance, Zhang's group confirmed that electron-deficient triazine-based COFs could afford high conversion and selectivity because the material can not only facilitate the generation and separation of charges, but also enrich the photocatalytically active sites.…”

Construction of Covalent Organic Frameworks via Multicomponent Reactions

“…Thus, the construction of high-quality chiral COFs requires the rational optimization of reaction conditions to balance crystallinity and optical purity. Fortunately, progress has been achieved in the synthesis of COFs under ambient conditions, and this field has now expanded to include chiral COFs . Additionally, protective groups, modulators, or tandem reactions may effectively increase COF crystallinity by decelerating framework formation, and this approach is expected to be extended to the MCR-based synthesis of chiral COFs in the near future.…”

Covalent Organic Frameworks as Porous Pigments for Photocatalytic Metal-Free C–H Borylation

“…Although COFs can act as a replacement for the homogeneous photocatalyst analogues, like inorganic metal-complexes[Ru­(bpy) 3 ]­(PF 6 ) 2 and Ir­(ppy) 3 , or organic dyes, such as 4CzIPN, Eosin Y, and acridinium, they have mainly been employed in water splitting, carbon dioxide reduction, and hydrogen evolution reactions . A few examples in organic synthesis include oxidation, oxidative hydroxylations, C–H functionalization, C–C, C–N, and, C–S cross-coupling reactions using metal-anchored (primarily) COF photocatalysts. However, metal-anchored COFs might contaminate the products with a trace amount of metal and suffer from reusability issues.…”