Construction of Crystalline Nitrone-Linked Covalent Organic Frameworks Via Kro''hnke Oxidation

Developingdiverse synthetic routes to prepare various crystallinecovalent organic frameworks (COFs) and enrich the family of COFs isvery important and highly desirable. In this research, we demonstratethat Kro''hnke oxidation (originally developed to prepare carbonylcompounds) can be employed as an efficient method to construct twocrystalline nitrone-linked COFs (CityU-1 and CityU-2) through theingenious design of the polynitroso-containing precursors as wellas the exquisite control of the polymerization conditions. The formationand structure of nitrone-based linkage units have been confirmed througha mode reaction. The as-obtained crystalline COFs have been characterizedby Fourier transform infrared and X-ray photoelectron spectroscopy,powder X-ray diffraction patterns, and scanning electron microscopy.Notably, CityU-1 exhibits a BET specific surface area of 497.9 m(2)g(-1) with an I-2 capture capacityof 3.0 g g(-1) at 75 & DEG;C. Our research would providemore chances to prepare various crystalline COFs for diverse applications.