Dawson-Type Polyoxometalates Functionalized Porphyrin-Based Covalent Organic Frameworks for Visible-Light-Driven...

Photocatalytic oxidation of sulfides to sulfoxides and detoxification of mustard gas simulant 2-chloroethyl ethyl sulfide (CEES) to nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) is an area of great interest in green chemistry. Herein, two hybrids based on Dawson-type polyoxometalate anions and porphyrin-based covalent organic frameworks, P₂W₁₈-COF (1) and P₂Mo₁₈-COF (2), (COF = porphyrin-based covalent organic frameworks), were synthesized via hydrothermal reaction and characterized by infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectra (DRS), etc. With powerful visible-light harvesting properties of porphyrin-based covalent organic frameworks (COFs) and abundant photocatalytic active sites provided by Dawson-type polyoxometalate, these hybrids exhibit outstanding photocatalytic activity in the oxidation of sulfides and in the detoxification of CEES under 10 W white light-emitting diode (LED) light irradiation with O₂ as an oxidant. Notably, P₂W₁₈-COF shows unparalleled photocatalytic efficiency, in which the conversion of methyl phenyl sulfide is 99% in 18 min and the degradation of CEES is 99% in 10 min. In addition, P₂W₁₈-COF can be recycled 12 times without decreasing the photocatalytic efficiency, marking the excellent durability of P₂W₁₈-COF as a heterogeneous catalyst. The photocatalytic mechanism reveals that O₂^•- arising from the electron transfer process and ¹O₂ resulting from the energy transfer process are present in the photocatalytic reaction.