Selective Oxidation Of Sulfides Research Articles

Precise Single-Atom Modification of Hybrid Lead Chlorides for Electron Donor-Acceptor Effect and Enhanced Photocatalytic Aerobic Oxidation.

Hybrid lead halides show significant potential in photocatalysis due to their excellent photophysical properties, but the atomically precise modification of their organic component to achieve synergistic interactions with the lead halide units remains a great challenge. Herein, for the first time, we have employed the crystal engineering strategy to construct a class of single-atom-substituted hybrid lead halides with electron donor-acceptor (D-A) effect. The lead halide frameworks consist of 1D linear [PbCl]+ chains as inorganic building units and benzoxadiazole/benzothiadiazole/ benzoselenadiazole-funtionalized dicarboxylates as linkers. The covalent bonding between the organic ligands with electron-withdrawing groups and the electron-rich lead halide units not only facilitate the charge separation, but also enhance structural robustness that is critical for photocatalysis. The D-A structured lead halides serve as highly efficient heterogeneous photooxidation catalysts, including aerobic oxidation of C(sp3)-H bonds, oxidative coupling of primary amines, oxidation of phenylboronic acids and selective oxidation of sulfides that are demonstrated in 30 examples. Importantly, these photooxidation reactions are able to be driven by natural sunlight and ambient air to afford quantitative yields. Moreover, our lead halide photocatalysts are successful to fix into a photocatalytic flow system, which enables the flow-type synthesis of high value-added photooxidation products on a gram scale.

A Heterogeneous Phosphomolybdate Nanocatalyst Utilizes Vitamin B1 to Promote Solvent‐Free H2O2 Sulfoxidation Selectivity

ABSTRACTCatalyst design and fabrication with safe and affordable components and methods is a high‐value‐added business. In this work, a vitamin‐based hybrid nanomaterial (PMoB1) is prepared by simple stirring of thiamine hydrochloride (vitamin B1, VB1) as an inexpensive commercially available biologically active compound with phosphomolybdic acid (PMo12) in acidic aqueous solution to catalyze selective oxidation of sulfides using aqueous H2O2. A small amount of this heterogeneous catalyst drives rapidly the sulfoxidation reaction under mild and solvent‐free conditions facilitating the product separation and reducing significantly the environmental impacts. The main factors of the catalytic reaction were optimized by the central composite design (CCD) method. The solid catalyst tolerates a wide range of pH and retained its structural integrity even at alkaline solution (pH = 11). PMoB1 composed of two VB1 and one PMo12 was found to be partially reduced based on 13P NMR and UV–Vis spectra. An amorphous structure with aggregated nanoparticles with sizes ranging between 50 and 70 nm and a specific surface area of 35 m2/g are important reasons for enhanced catalytic activity and selectivity. Nevertheless, non‐covalent interactions such as hydrogen bonding and the π–π stacking can also significantly affect the catalyst performance. Given the scavenging tests and spectral evidences, a non‐radical mechanism involving peroxo species is postulated. The catalysis is shown to be truly heterogeneous while the solid catalyst largely maintains its structural integrity during the recycling test.

Tunable and selective transformation of aromatic thioether enabled by regulating active species under visible light irradiation

Through effective regulation of active species in photocatalytic process, the oxidation or C(sp3)‐S bond cleavage upgrading of widespread aryl alkyl sulfides under mild conditions was successfully achieved by using a pyridinium photocatalyst. Benefiting from the excellent redox ability of the photocatalyst, the electron transfer between the pyridinium molecule and the substrate, molecular oxygen, or counter‐anion effectively promotes the conversion and upgrading of the substrate thioether. Among them, the efficient generation of reactive oxygen species (ROS) enables the highly selective oxidation of sulfides to sulfoxides under visible light and air atmosphere. More importantly, the chlorine radical (Cl•) generated by electron transfer, reported for the first time, contributes to the cleavage of C(sp3)‐S bonds, achieving the transformation of aryl alkyl sulfides to disulfides. By harnessing the superior photocatalytic ability of pyridinium molecules, this work not only achieves the highly selective conversion of thioether by taming the active species in the photocatalytic process, but also sheds light on the untapped potential of chlorine radicals in the field of C(sp3)‐S bond activation and cleavage.

Precise Single‐Atom Modification of Hybrid Lead Chlorides for Electron Donor‐Acceptor Effect and Enhanced Photocatalytic Aerobic Oxidation

Hybrid lead halides show significant potential in photocatalysis due to their excellent photophysical properties, but the atomically precise modification of their organic component to achieve synergistic interactions with the lead halide units remains a great challenge. Herein, for the first time, we have employed the crystal engineering strategy to construct a class of single‐atom‐substituted hybrid lead halides with electron donor‐acceptor (D‐A) effect. The lead halide frameworks consist of 1D linear [PbCl]+ chains as inorganic building units and benzoxadiazole/benzothiadiazole/ benzoselenadiazole‐funtionalized dicarboxylates as linkers. The covalent bonding between the organic ligands with electron‐withdrawing groups and the electron‐rich lead halide units not only facilitate the charge separation, but also enhance structural robustness that is critical for photocatalysis. The D‐A structured lead halides serve as highly efficient heterogeneous photooxidation catalysts, including aerobic oxidation of C(sp3)‐H bonds, oxidative coupling of primary amines, oxidation of phenylboronic acids and selective oxidation of sulfides that are demonstrated in 30 examples. Importantly, these photooxidation reactions are able to be driven by natural sunlight and ambient air to afford quantitative yields. Moreover, our lead halide photocatalysts are successful to fix into a photocatalytic flow system, which enables the flow‐type synthesis of high value‐added photooxidation products on a gram scale.

Boosting Electrocatalytic Performance of Sulfide Oxidation on Polyoxomolybdates with Synergistic Effects of CNT‐Doped Aerogel Foams

AbstractThe meticulous design of highly efficient indirect electrocatalysts with value‐added conversion properties remains a substantial challenge within the realm of organic catalysis. While polyoxometalates (POMs) serve as crucial active centers in catalytic modeling systems for chemical materials, their exploration in electrocatalytic organic molecular transformations is hindered by kinetic barriers. Therefore, an efficient protocol is established for the synthesis of electrocatalysts utilizing polyoxomolybdates (CuMo6) immobilized on aerogel foams (CMC). The electrical conductivity and electrocatalytic activities of the electrocatalyst (CuMo6/CNT@CMC) can be readily enhanced by adjusting the microenvironment between the CuMo6 and CMC using carbon nanotubes (CNT). Controlled experiments demonstrate that the CuMo6/CNT@CMC electrocatalyst for the oxidation of sulfide achieves an impressive Faradaic Efficiency (FE) exceeding 95% under ambient conditions, while the working potential is markedly lower than that of reported heterogeneous electrocatalysts. Combined experimental and theoretical analyses suggest that the modulated electronic synergistic interaction between the Cu‐assisted Mo sites and CNT within foam favors the appropriate binding of PhCH3S+• intermediates, thereby promoting the selective oxidation of sulfides. This study paves the way for the utilization of polyoxometalate‐based materials with simple synthesis methods for various electrocatalytic applications.

Construction of Cobalt-Containing Polyoxovanadate-Based Inorganic-Organic Hybrids as Heterogeneous Catalysts for the Selective Oxidation of Sulfides.

In order to develop efficient catalysts for the selective oxidation of sulfides, in this work, two polyoxovanadate-based inorganic-organic hybrids, [Co(H2O)3(3-bpfb)0.5(V2O6)]·(3-bpfb)0.5 (1) and [Co(H2O)2(4-bpfb)0.5(V2O6)] (2) [3-bpfb = N, N'-bis(3-pyridylformamide)-1, 4-benzenediamine, 4-bpfb = N, N'-bis(4-pyridylformamide)-1, 4-benzenediamine], were isolated under hydrothermal conditions. The structures of 1 and 2 embodied two kinds of different cobalt-containing polyoxovanadate-based inorganic chains. Compound 1 contained a one-dimensional inorganic zigzag chain created by the aggregation of {V2O6} clusters with each other, on which Co (II) ions were fixed. But it was an inorganic dimeric chain constructed from two linear {V2O6} cluster-based chains gathered by Co (II) ions in 2. The 3-bpfb and 4-bpfb ligands, as the bidentate linkers, coordinated with two Co (II) ions from adjacent chains to organize them into two-dimensional layers. The hydrogen bonds made important contributions to the formation of supramolecular structures of the two compounds. The two compounds served as heterogeneous catalysts and exhibited efficient activity for the selective oxidation of sulfide to sulfoxide and could be reused at least six times without loss of catalytic activity and stability.

Benzothiadiazole-Based Ordered Mesoporous Polymer as a Versatile, Metal-Free Heterogeneous Photocatalyst.

Visible-light active heterogeneous organophotocatalysts have recently gained considerable interest in organic synthetic community. Ordered mesoporous polymers (OMPs) are highly promising as heterogeneous alternative to traditional precious metal/organic dyes-based photocatalysts. Herein, we report the preparation of a benzothiadiazole functionalized OMPs (BT-MPs) through a "bottom-up" strategy. High ordered periodic porosity, large surface area, excellent stability and rational energy-band structures guarantee the high catalytic activity of BT-MPs. As a result, at least six conversions, e. g., the [3+2] cycloaddition of phenols with olefins, the selective oxidation of sulfides, the C-3 thiocyanation of indole and the aminothiocyanation of β-keto ester, could be promoted smoothly by BT-MPs. In addition, BT-MPs was readily recovered with well maintaining its photocatalytic activity and could be reused for at least eight times. This study highlights the potential of exploiting photoactive OMPs as recyclable, robust and metal-free heterogeneous photocatalysts.

Synthesis of flower-like covalent organic frameworks for photocatalytic selective oxidation of sulfide

BackgroundCovalent organic frameworks (COFs)-based photocatalysts have garnered significant attention for their potential in highly efficient and selective sulfide oxidation. However, the current synthesis methods of COF-based catalysts involve complex multi-step procedures, and better methods need to be upgraded for synthesis. MethodsIn this study, a flower-like COF-based photocatalyst (f-COFs) was synthesized by one-pot method at room temperature using zinc chloride (ZnCl2) as catalyst. The photocatalytic performance of f-COFs was investigated using methyl phenyl sulfide as substrate. Significant FindingsZinc ions remain on the f-COFs synthesized by this method. EDX analysis and XPS techniques were used to confirm the presence of zinc ions. The presence of zinc ions controls the self-assembly of COFs to form unique flower-like microstructure. Its flower-like microstructure provides a strong light absorption capacity. At the same time, the recombination of charge is inhibited, thus promoting the energy and electron transfer during the photocatalytic reaction. These properties allow reactive oxygen species to be prevalent in the reaction process of f-COFs as a photocatalyst, driving the conversion of methyl phenyl sulfide to sulfoxide within 5 h with excellent performance of 95 % conversion and 99 % selectivity.

Magnetic curcumin–copper graphene oxide as facile and recyclable heterogeneous nanocatalyst for preparation of polyhydroquinolines and sulfoxides

In this research project, a versatile procedure has been designed for the preparation of supported copper@curcumin on magnetic graphene oxide nanoparticles (GO@Fe3O4@Cur–Cu). The structure of prepared nanocatalyst was characterized by several techniques including; Fourier transform infrared, powder X-ray diffraction, thermal gravimetric analysis, energy dispersive X-ray analysis, inductively coupled plasma optical emission spectroscopy, vibrating sample magnetometer, transmission electron microscopy, and scanning electron microscopy analyses. The catalytic properties of GO@Fe3O4@Cur–Cu were examined for the efficient synthesis of polyhydroquinolines as well as the preparation of sulfoxides through selective oxidation of sulfides in the presence of hydrogen peroxide.

Integrating Polyoxometalates and Silver Clusters into Atomically Precise Molecular Heterojunction.

The Ag cluster-POM assemblies have been shown to possess interesting and potentially useful properties. However, there is no precedent example of atomically precise Ag cluster-POM assemblies showing heterojunction effects in photocatalysis. Herein, the synthesis and total structure determination of the periodically distributed molecular heterojunction [Ag12(SCy)6(CH3CN)12(PW12O40)]n (Ag12-PW12) are reported. The assembly of Ag/W clusters into 3D network can endow the resulting binary structure with an aesthetic topology and unique physicochemical properties. More remarkably, the incorporation of Ag12 cluster with PW12 can efficiently facilitate the separation of photogenerated electrons and holes, thus significantly promoting the catalytic efficiency in selective oxidation of sulfides. The Ag12-PW12 heterojunction can be recovered and reused five times with no drastic change in the catalytic performance. This research is expected to assist in the rational design of cluster-based heterojunction catalysts. The increase of catalytic activity of the Ag12-PW12 assembly in comparison with the unassembled Ag12 and PW12 clusters is attributed to the synergistic effect of Ag12 and PW12 clusters, offering the splendid opportunity for deciphering structure-reactivity relationship of heterostructure-coupled photosystem.

Template Synthesis of Cyclometalated Macrocycle Iridium(III) Complexes Based on Photoinduced C-N Cross-Coupling Reactions In Situ.

The synthesis of metal macrocycle complexes holds paramount importance in coordination and supramolecular chemistry. Toward this end, we report a new, mild, and efficient protocol for the synthesis of cyclometalated macrocycle Ir(III) complexes: [Ir(L1)](PF6) (1), [Ir(L2)](PF6) (2), and [Ir(L3)](PF6) (3), where L1 presents 10,17-dioxa-3,6-diaza-2(2,8),7(8,2)-diquinolina-1,8(1,4)-dibenzenacyclooctadecaphane, L2 is 10,13,16,19,22,25-hexaoxa-3,6-diaza-2(2,8),7(8,2)-diquinolina-1,8(1,4)-dibenzenacyclohexacosaphane, and L3 is 4-methyl-10,13,16,19,22,25-hexaoxa-3,6-diaza-2(2,8),7(8,2)-diquinolina-1,8(1,4)-dibenzenacyclohexacosaphane. This synthesis involves the preassembly of two symmetric 2-phenylquinoline arms into C-shape complexes, followed by cyclization with diamine via in situ interligand C-N cross-coupling, employing a metal ion as a template. Moreover, the synthetic yield of these cyclometalated Ir(III) complexes, tethered by an 18-crown-6 ether-like chain, is significantly enhanced in the presence of K+ ion as a template. The resultant cyclometalated macrocycle Ir(III) complexes exhibit high stability, efficient singlet oxygen generation, and superior catalytic activity for the aerobic selective oxidation of sulfides into sulfoxides under visible light irradiation in aqueous media at room temperature. The photocatalyst 2 demonstrates recyclability and can be reused at least 10 times without a significant loss of catalytic activity. These results unveil a new and complementary approach to the design and in situ synthesis of cyclometalated macrocycle Ir(III) complexes via a mild interligand-coupling strategy.

Fully Conjugated Covalent Organic Framework Nanosheets for Visible-Light-Driven Organic Synthesis in Water.

Covalent organic framework (COF) nanosheets have recently garnered great attention as a new class of functional materials. As one of the sustainable processes, however, the photocatalytic organic synthesis in water has not been investigated using COF nanosheets as a photocatalyst to date. Herein, we reported the synthesis of a fully conjugated COF nanosheets with carboxyl functional group through a cooperative strategy of chemical exfoliation and group transformation. The new COF nanosheets was found to be an efficient heterogeneous photocatalyst for a wide range of organic synthesis including selective oxidation of sulfides and oxidative coupling of benzylamines in water under visible-light illumination. This work contributes a new roadmap for the design and synthesis of functional COF-based nanosheets, but also further extends the application boundary of the ultrathin COF nanosheets.

Correction to “Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides”

Correction to “Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides”

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

Selective oxidation of sulfides to sulfoxides is of great significance in the synthesis of pharmaceuticals, desulfurization of fuels, and detoxification of sulfur mustard chemical warfare agents. Designing selective catalysts to achieve the efficient transformation of sulfides to sulfoxides is thus highly desired. Herein, we report three transition metal-complex-functionalized polyoxovanadates, [Zn2(BPB)2][V4O12]·0.5BPB·H2O (1), [Ni(BPB)(H2O)][V2O6]·2H2O (2), and [Co(HBPB)2][V4O12] (3) (BPB = 1,4-bis(pyrid-4-yl)benzene)), and explore their applications for selective oxidation of sulfides using H2O2 as an oxidant. All three compounds were catalytically effective for the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide, with 1 being best-performing with complete conversion and a selectivity of 96.7%. In the selective oxidation of a series of aromatic and aliphatic sulfides to corresponding sulfoxides, 1 also showed satisfactory performance; in particular, the chemical warfare agent stimulant 2-chloroethyl ethyl sulfide can be completely and selectively oxidized to the nontoxic 2-chloroethyl ethyl sulfoxide within 20 min at room temperature. Catalyst 1 can be recycled and reused at least six times with uncompromised performance. The perfect performance of 1 is attributed to the synergistic effect of coordinatively unsaturated V and Zn sites in bimetallic oxide, as revealed by comparative structural and catalytic studies.

Robust cooperative of cadmium sulfide with highly ordered hollow microstructure coordination polymers for regulating the photocatalytic performance

Accurately controlling and achieving selective reactivity at difficult-to-access reaction sites in organic molecules is challenging owing to the similar local and electronic environments of multiple reaction sites. In this work, we regulated multiple reaction sites in a highly selective and active manner using cobalt coordination polymers (Co-CP) 1 and 1a with various particle sizes and morphologies ranging from large granular to ordered hollow hemispheres by introducing sodium dodecyl sulfate (SDS) as a surfactant. The size and morphology of the catalysts could be tuned by controlling the amount of SDS. An SDS concentration of 0.03 mmol generated 1a having a highly ordered hollow hemispherical microstructure with a well-defined platform as a pre-made building unit. Cadmium sulfide (CdS), as a typical photocatalyst, was subsequently uniformly anchored in-situ on the premade building unit 1a to produce CdS@1a composites, that inherited the originally ordered hollow hemispherical microstructure while integrating CdS as well-dispersed catalytic active sites. Furthermore, the well-established CdS@1a composites were used as photocatalysts in selective oxidation reactions under air atmosphere with blue irradiation. The CdS0.109@1a composite with unique structural characteristics, including uniformly distributed and easily accessible catalytic sites and excellent photoelectrochemical performance, served as a highly efficient heterogeneous photocatalyst for promoting the selective oxidation of sulfides to sulfoxides as the sole products. This work presents an approach for fabricating CPs as premade building units that function as well-defined platforms for integration with photocatalysts, enabling tuning of the structure-selectivity-activity relationships.

Mild selective photochemical oxidation of an organic sulfide using OxP-polyimide porous polymers as singlet oxygen generators

ABSTRACT A series of porous organic polymers based on a singlet oxygen generating oxoporphyinogen (‘OxP’) has been successfully prepared from a pseudotetrahedral OxP-tetraamine precursor (OxP(4-NH 2 Bn) 4 ) by its reaction with tetracarboxylic acid dianhydrides under suitable conditions. Of the compounds studied, those containing naphthalene (OxP-N) and perylene (OxP-P) spacers, respectively, have large surface areas (~530 m2 g−1). On the other hand, the derivative with a simple benzene spacer (OxP-B) exhibits the best 1O2 generating capability. Although the starting OxP-tetraamine precursor is a poor 1O2 generator, its incorporation into OxP POPs leads to a significant enhancement of 1O2 productivity, which is largely due to the transformation of NH2 groups to electron-withdrawing diimides. Overall 1O2 production efficacy of OxP-POPs under irradiation by visible light is significantly improved over the common reference material PCN-222. All the materials OxP-B, OxP-N and OxP-P promote oxidation of thioanisole involving conversion of ambient triplet state oxygen to singlet oxygen under visible light irradiation and its reaction with the sulfide. Although the reaction rate of the oxidation promoted by OxP POPs is generally lower than for conventional materials (such as PCN-222) or previously studied OxP derivatives, undesired overoxidation of the substrate to methyl phenyl sulfone is suppressed. For organic sulfides, selectivity of oxidation is especially important for detoxification of mustard gas (bis(2-chloroethyl)sulfide) or similarly toxic compounds since controlled oxidation leads to the low toxicity bis(2-chloroethyl)sulfoxide while overoxidation leads to intoxification (since bis(2-chloroethyl)sulfone presents greater toxicity to humans than the sulfide substrate). Therefore, OxP POPs capable of promoting selective oxidation of sulfides to sulfoxides have excellent potential to be used as mild and selective detoxification agents.

Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides

Thermoresponsive Polymeric Nanoparticles as Efficient Pickering Interfacial Catalysts for Selective Oxidation of Sulfides

π-conjugated chromophore functionalized high-nuclearity titanium-oxo clusters containing structural unit of anatase for photocatalytic selective oxidation of sulfides

π-conjugated chromophore functionalized high-nuclearity titanium-oxo clusters containing structural unit of anatase for photocatalytic selective oxidation of sulfides

Hollow anatase TiO2 tetrakaidecahedral crystals with an active {001}/{110} redox interface toward high-performance photocatalytic activity.

The existence of the oxidation/reduction interface can promote the performance of a photocatalyst, due to its effect on the separation of photogenerated carriers and the surface reactivity. However, it is difficult to construct two sets of oxidation/reduction interfaces in a single crystal and compare their separation efficiency for photogenerated carriers. Introducing a high proportion of active facets into the co-exposed facets is even more challenging. Herein, a hollow anatase TiO2 tetrakaidecahedron (HTT) with two sets of oxidation/reduction interfaces ({001}/{101} and {001}/{110}) is synthesized by directional chemical etching. Theoretical and experimental results indicate that the {001}/{110} interface is a dominant oxidation/reduction interface, showing a better promotion on the separation of photogenerated carriers than the {001}/{101} interface. In the HTT, the ratio of dominant {001}/(110) is increased and the proportion of the active {110} facet is about 40% (generally about 15%). Therefore, the HTT shows excellent catalytic activity for photocatalytic reductive (hydrogen production) and oxidative (selective oxidation of sulfides) reactions. The HTT also demonstrates favorable photocatalytic activity for the cross-dehydrogenative coupling reaction, where both photogenerated electrons and photogenerated holes are involved, further verifying its high separation efficiency of photogenerated carriers and surface reactivity. This work provides an important guideline for developing advanced structures with a predetermined interface toward desired applications.

Extending 2D covalent organic frameworks by inserting anthracene for promoted white-light-mediated photocatalysis

A novel anthracene-based covalent organic framework was synthesized, with potential application for white light-induced oxidative coupling of amines and selective oxidation of sulfides, both of which yielded remarkable conversion and selectivity.