Dawson-Type Polyoxometalates Functionalized Porphyrin-Based Covalent Organic Frameworks for Visible-Light-Driven Oxidation of Sulfides and Detoxification of Mustard Gas Simulants
Qingshan Zhu, Haiyan An, Jie Fu, Hao Sun, Yaying Zhang, Tieqi Xu
Abstract
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, P 2 W 18 –COF ( 1 ) and P 2 Mo 18 –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 O 2 as an oxidant. Notably, P 2 W 18 –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, P 2 W 18 –COF can be recycled 12 times without decreasing the photocatalytic efficiency, marking the excellent durability of P 2 W 18 –COF as a heterogeneous catalyst. The photocatalytic mechanism reveals that O 2 •– arising from the electron transfer process and 1 O 2 resulting from the energy transfer process are present in the photocatalytic reaction.