Visible-Light-Responsive 2D Photocatalysts Assembled by Evans–Showell-Type POMs and Metalloviologen Frameworks for Sulfide–Sulfoxide Transformation

Abstract

Sulfide−sulfoxide aerobic photo-oxidation is of great interest in organic and medicinal chemistry; however, developing efficient and facile heterogeneous photocatalytic systems without additional additives remains challenging. Herein, we intentionally designed and synthesized two polyoxometalate (POM)-based metalloviologen frameworks, formulated asprepared by the mild one-step synthesis strategy and characterized in detail. X-ray single-crystal diffraction analysis shows that they present a two-dimensional layered structure formed by two parallel metalloviologen layers pillared by dimeric Evans−Showell-type POMs. The connection of POM to the metalloviologen framework enables easier flow of electrons to the POM port, which can theoretically further induce O 2 to generate reactive oxygen species (O 2•− ) to oxidize substrates to form target products. As expected, both 1 and 2 exhibit outstanding photocatalytic activity in the oxidation of sulfides. Within 6 h, methyl phenyl sulfide can be quantitatively converted into methyl phenyl sulfoxide. The in-depth mechanism reveals that there is also a synergistic energy-transfer pathway in the catalytic system in addition to the electron-transfer pathway. In addition, the corresponding catalytic activity and structure can be well maintained after at least 10 cycle experiments.

Visible‐Light‐Responsive Polyoxometalate@Metal‐Organic Frameworks Involving Ir Metalloligands for Highly Selective Photocatalytic Oxidation of Sulfides to Sulfoxide

“…The authors have cited additional references within the Experimental Section and Supporting Information. [11,15,27,71,[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93]…”

“…[12][13][14] Therefore, the photo-oxidation pathway utilizing visible light and molecular oxygen as oxidants has attracted much attention due to its mild reaction conditions and environmentally friendly features. [15] Polyoxometalates (POMs) are a category of metalÀ oxygen cluster compounds that comprise the highest oxidation state of the early transition metal (such as Mo VI , W VI , V V , Ta V , and Nb V ). They have been commonly exploited in all kinds of photocatalytic reactions because of their structural diversity, and semiconductor-like properties.…”

Modulating the Catalytic Properties of Polyoxovanadates with Transition-Metal-Complex Units for Selective Oxidation of Sulfides

“…On the one hand, sulfoxides are important intermediates in the making of a great variety of high-value chemicals including pharmaceuticals (Scheme a). , On the other hand, sulfide-to-sulfoxide transformation is an effective strategy for desulfurizing crude oil (Scheme b) − and for detoxicating chemical warfare agents (CWAs) such as bis­(2-chloroethyl) sulfidea notorious vesicant (Scheme c). , Not surprisingly, great efforts have been devoted to improving the practice of this important chemical transformation. One particularly important goal is to replace toxic oxidants, for example, the traditional and stoichiometrically used CrO 3 , with ecologically more friendly ones including most desirably molecular oxygen and hydrogen peroxide . However, the operation of the greener oxidants generally requires the use of a catalyst.…”

A reduced polyoxometalate-encapsulated organo cobalt modified phosphate framework for improving photocatalytic reduction of CO2

“…Polyoxometalates (POMs), which constitute a subfamily of metal oxide cluster materials composed of earth-abundant elements, possess vital value in various fields due to their well-defined structures and diverse components. 10–15 Because of the semiconductor characteristics, strong light absorption, and excellent redox capabilities, it is viable for POMs to undergo reversible and continuous electron transport rapidly in catalytic reactions including water splitting and the photocatalytic CO 2 RR without structural changes. Furthermore, another significant characteristic is that POMs have a rich surface with oxygen atoms and a high number of negative charges, which always display diverse coordination modes that can coordinate with different types of transition metals forming ligand-to-metal charge transfer bands so as to play a role in regulating the absorbance and energy levels.…”