Oxidation Of Organic Sulfides Research Articles

Phosphonate-Substituted Pyrazinoporphyrin - a General Photocatalyst for Efficient Sulfoxidation.

An exceptional efficiency of pyrazine-annelated porphyrin as a general photocatalyst for the oxidation of organic sulfides is demonstrated. It is shown that phosphonate-substituted pyrazinoporphyrin 2H-1 brings together sufficient photostability and high efficiency in the aerobic photooxidation of a series of various sulfides. The influence of the reaction conditions onto the efficiency of homogeneous sulfide photooxidation in the presence of the photosensitizer (PS) was investigated and strong dependence on the solvent system was observed. The use of methanol is required for the photocatalytic sulfoxidation and the ratio of the alcohol/other solvent can significantly affect the conversion and selectivity of the reaction. The application of the prepared PS in 0.001 mol % loading allowed achieving complete conversion (97-100 %, turnover number up to 1,00,000, turnover frequency up to 6250 h-1) of substrates bearing substituents of different nature, namely aromatic and aliphatic sulfides with donor or acceptor substituents and substituents prone to oxidation, as well as cyclic sulfides. The selectivity of the of the corresponding sulfoxides formation of 96-100 % was revealed. Finally, a gram-scale synthesis of several sulfoxides was successfully performed with the PS under investigation, providing desired products in 66-96 % yield with over 98 % purity.

Pyrene- and Benzothiadiazole-Based Mixed-Ligand D–A Metal–Organic Framework for the Enhancing Photocatalytic Aerobic Oxidation of Organic Sulfides

Pyrene- and Benzothiadiazole-Based Mixed-Ligand D–A Metal–Organic Framework for the Enhancing Photocatalytic Aerobic Oxidation of Organic Sulfides

Single walled carbon nanotubes covalently functionalized by a ruthenium complex for photocatalytic oxidations

The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is presented, thus yielding the sample SWNT-Ru. To do that, an-amino decorated phenanthroline is bonded to the nanotube by means of the diazonium chemistry protocol, providing anchoring points for discrete organometallic units as depicted by the solid characterization techniques employed. The hybrid material, able to emit upon excitation, is active in the visible light-driven photocatalytic oxidation of organic sulfides to sulfoxides. SWNT-Ru presents a wide scope being able to convert more than 10 substrates with different characteristics, including added-value chemicals, with a stable performance over more than 6 cycles without metal leaching and enhanced activity compared to related homogeneous complexes. A versatile character is also demonstrated since this hybrid catalyst follows both possible photooxidation mechanisms.

Exceptional functionalized ionic liquid@metal–organic framework: A high-efficiency desulfurization platform for organic sulfide oxidation by reactive oxygen species

There is a challenge with designing catalysts that simultaneously possess active sites for catalyzing the generation of reactive oxygen species (ROSs) and effectively overcoming mass transfer resistance in oil–water biphasic systems. In this study, a novel, highly efficient oxidative desulfurization (ODS) strategy is proposed that uses an ILs-loaded metal–organic framework (MOF) coupled material as a catalyst. The IL@MOF ([Hnmp]HSO4@MIL-125(Ti)) coupled material prepared by loading [Hnmp]HSO4 onto MIL-125(Ti) has catalytic-adsorption synergistic capability. It demonstrated outstanding oxidative desulfurization performance by achieving nearly a 100 % removal of dibenzothiophene (DBT) from model oil with a dosage of 0.04 g IL@MOF per 10 mL of model fuel under mild conditions (50 °C, 10 min). By comparing the experimental results with the characterization data, it is suggested that [Hnmp]HSO4@MIL-125(Ti) converts superoxide radicals (•O2−) into 1O2 through oxygen vacancies (Ov) and that the catalytic action of Ti on the oxidation of DBT is primarily based on a 1O2-driven non-free radical mechanism. [Hnmp]HSO4@MIL-125(Ti) serves as a favorable medium for contact to be made between ROSs and sulfides, which indicates an efficient catalytic-adsorption synergy.

Thiazole-linked isomeric covalent organic frameworks for divergent photocatalysis: Selective oxidation of organic sulfides

The photocatalysis of covalent organic frameworks (COFs) is underpinned by their inherent structures in which the linkage plays a vital role in determining the activity. The transformation of imine into thiazole leads to isomeric structures owing to the different orientations of linkages. Here, two thiazole-linked COFs, COF-TZ-1 and COF-TZ-2, are constructed from two imine-linked COFs, COF-IM-1 and COF-IM-2, with the imine N next to the linker triphenylbenzene and triphenyltriazine, respectively. Despite better absorption, COF-TZ-1 possesses inferior optoelectronic properties to COF-TZ-2. Besides, the dipole moment of COF-TZ-2 is twice that of COF-TZ-1. COF-TZ-2 is much better than COF-TZ-1 for blue light photocatalytic selective oxidation of organic sulfides with O2 under blue light irradiation. Furthermore, the facile adsorption sites of O2 are verified by density functional theory calculations, and the generation of superoxide is tracked over COF-TZ-2. This work highlights that subtle variations of COFs can lead to divergent photocatalysis.

Expanding Olefin-Linked Covalent Organic Frameworks toward Selective Photocatalytic Oxidation of Organic Sulfides.

Olefin-linked covalent organic frameworks (COFs) have exhibited great potential in visible-light photocatalysis. In principle, expanding fully conjugated COFs can facilitate light absorption and charge transfer, leading to improved photocatalysis. Herein, three olefin-linked COFs with the same topology are synthesized by combining 2,4,6-trimethyl-1,3,5-triazine (TMT) with 1,3,5-triformylbenzene (TFB), 1,3,5-tris(4-formylphenyl)benzene (TFPB), and 1,3,5-tris(4-formylphenylethynyl)benzene (TFPEB), namely, TMT-TFB-COF, TMT-TFPB-COF, and TMT-TFPEB-COF, respectively. From TMT-TFB-COF to TMT-TFPB-COF, expanding phenyl rings provides only limited expansion for π-conjugation due to the steric effect of structural twisting. However, from TMT-TFPB-COF to TMT-TFPEB-COF, the insertion of acetylenes eliminates the steric effect and provides more delocalized π-electrons. As such, TMT-TFPEB-COF exhibits the best optoelectronic properties among these three olefin-linked COFs. Consequently, the photocatalytic performance of TMT-TFPEB-COF is much better than those of TMT-TFB-COF and TMT-TFPB-COF on the oxidation of organic sulfides into sulfoxides with oxygen. The desirable reusability and substrate compatibility of the TMT-TFPEB-COF photocatalyst are further confirmed. The selective formation of organic sulfoxides over TMT-TFPEB-COF under blue light irradiation proceeds via both electron- and energy-transfer pathways. This work highlights a rational design of expanding the π-conjugation of fully conjugated COFs toward selective visible-light photocatalysis.

Activation of C(SP3)–H Bonds Promoted Oxidation of Sulfides by O2 Under Catalyst-Free Conditions

Oxidation of organic sulfides is a significant reaction due to its application in many fields. Herein, we have developed a novel catalyst-free oxidation of organic sulfides by O2 under relatively mild conditions. The choice of the procedure was based on the well-acknowledged reactivity of the active C(sp3)-H bond of organic compounds to form the corresponding alkyl carbon free radicals (Rand#183;) in the presence of O2. The results showed that hydrocarbons such as tetrahydronaphthalene (THN) and cumene possessing the active C(sp3)-H bonds due to their lower bond dissociation energy (BDE), as a solvent, markedly promoted this catalyst-free sulfoxidation. It has been proved that reactive oxygen species (ROS) in this reaction are alkyl-peroxide radicals that are produced from Rand#183;, which is derived from the homolytic cleavage of the active C(sp3)-H bond with the help of heating and dioxygen, and further its activation of molecular oxygen. On this basis, combined with the DFT calculation of the activation energy of two reaction pathways, a possible reaction mechanism is proposed. The work provided a green synthesis approach of sulfoxide and sulfone compounds, and a scientific basis for a green process of ultra-deep desulfurization of fuel oils.

A doubly interpenetrated perylene diimide-based zirconium metal–organic framework for selective oxidation of sulfides powered by blue light

A doubly interpenetrated perylene diimide-based zirconium metal–organic framework is developed as a heterogeneous photocatalyst for selective photocatalytic oxidation of organic sulfides powered by blue light.

Selective oxidation of sulfides by pyrene-π-anthraquinone conjugated microporous polymer photocatalysis

Enabled by tailorability and aromaticity, conjugated microporous polymers (CMPs) have become increasingly important in photocatalysis. Both pyrene and anthraquinone are essential building blocks of burgeoning photocatalytic materials like CMPs. Herein, alkynyl groups are embedded between pyrene and anthraquinone, affording Py-π-AQ-CMP. Theoretical calculation indicates that the insertion of alkynyl groups adjusts steric hindrance and ameliorates the planar π-conjugation. Notably, the extended π-conjugation generates a narrower band gap and more extensive optical response, enabling Py-π-AQ-CMP with superior charge carrier’s mobility. Gratifyingly, Py-π-AQ-CMP photocatalysis could enable the highly selective oxidation of organic sulfides in methanol. Significantly, driven by blue light, Py-π-AQ-CMP delivers almost twice of the efficiency of Py-AQ-CMP, a CMP without the alkynyl π-bridge. The mechanistic investigation suggests both electron and energy transfers participate in the activation of dioxygen for the oxidation of sulfides. This work highlights that inserting a π-bridge could afford high-performance photocatalysts of CMPs.

Preparation of polymeric ionic liquid-coated magnetic nanoball catalyst and coupling peroxymonosulfate for catalytic oxidation desulfurization at room temperature

A heterogeneous catalyst was prepared by wrapping a poly 3-butyl vinylimidazole cobalt chloride ionic liquid (P[BVIM]CoCl3) around the surface of Fe3O4@SiO2 magnetic nanoballs. This catalyst was coupled with the oxidant peroxymonosulfate (PMS) for extraction catalytic oxidation desulfurization (ECODS). The prepared desulfurization catalyst had superparamagnetic properties, with a saturation magnetization of 32.5 emu/g. Moreover, this caalyst was multi-porous material, ans it had a specific surface area and pore volume of 8.14 m2/g and 0.018 cc/g, respectively. The average pore diameter of catalyst was 3.9 nm. The optimal experimental conditions were as follows: the initial sulfur content of the oil was 500 ppm, the catalyst dosage was 30 mg, PMS (20 wt%) dosage was 0.6 g, the ACN dosage was 2 g, and the oil sample size was 6 g. After 20 min, a sulfur removal rate of over 98 % was achieved at 20 °C. Furthermore, the unpurified catalyst still maintained high desulfurization activity after being used for 5 times, demonstrating good stability. The desulfurization mechanism was divided into two steps: first, DBT was oxidized to DBTO by SO4− free radicals, and second, the DBTO was further oxidized to DBTO2 by OH free radicals in a tandem reaction. The reaction rates for the two steps at 20 °C were 0.0144 sec−1 and 0.00115 sec−1, respectively. The activation energies associated with these steps were 65.65 kJ/mol and 105.22 kJ/mol, respectively. The quencher t-butanol had no effect on the first step but significantly inhibited the second step, meaning that DBTO became the main oxidation product. One potential application of this study is the utilization of t-butanol to regulate the oxygen content in organic sulfide oxidation products.

Blue light photocatalytic oxidation of sulfides to sulfoxides with oxygen over a thiazole-linked 2D covalent organic framework

With permanent porosity and intrinsic crystallinity, covalent organic frameworks (COFs) have great potential for solar energy conversions. However, the crystallinity of COFs necessitates reversible linkages like imine, leading to inadequate chemical stability of COFs as photocatalysts. To overcome this inadequacy, post-synthetic modifications (PSMs) transform an imine-linked COF, TTI-COF, into a thiazole-linked COF, TTT-COF. The morphology and crystallinity of TTT-COF are similar to that of TTI-COF. Compared to TTI-COF, TTT-COF secures evident amelioration of stability and optoelectronic properties supported by both experiments and theoretical calculations. Consequently, these two COFs are exploited for the photocatalytic oxidation of organic sulfides. Under blue light-emitting diode irradiation, TTI-COF marginally impels the reaction. In contrast, TTT-COF emerges with significantly better activity for selective oxidation of organic sulfides with oxygen in ethanol. This work sheds light on the transformative power of PSMs for tailoring COFs in visible light photocatalysis for oxidations.

Merging benzotrithiophene covalent organic framework photocatalysis with TEMPO for selective oxidation of organic sulfides

Merging benzotrithiophene covalent organic framework photocatalysis with TEMPO for selective oxidation of organic sulfides

New application of an old dye: Bay-annulated indigo (BAI) as an organic photocatalyst for the oxidation of organic sulfides

Bay-annulated indigo (BAI), an old red dye first produced in 1914, which shows good performance as electron-accepting units in photovoltaic and semiconducting applications, was utilized as an organic photocatalyst for the first time. Under the irradiation of blue LEDs, organic sulfides can be selectively oxidized to corresponding sulfoxides with good to excellent yields. In addition, the photocatalytic oxidations of arylboronic acids and 2,3-dihydroquinazolinone derivatives were also investigated, indicating that it is a very promising organic photocatalyst for much more applications.

Reactivity Tuning of Metal‐Free Artificial Photoenzymes through Binding Site Specific Bioconjugation

AbstractThe design and development of artificial metal‐free photoenzymes aims to combine the selectivity of enzymatic reactions with the benefits of modern synthetic photocatalysts. Removing the need for rare earth metals and allowing for milder reaction conditions, leading to a more sustainable catalytic system. Here, we present the design of a novel artificial photoenzyme by integrating an organophotocatalytic moiety based on a donor‐acceptor design into a steroid carrier protein (SCP‐2L). SCP‐2L possesses a hydrophobic tunnel facilitating substrate binding in aqueous media. The photocatalyst was site‐selectively bound to three SCP‐2L variants, possessing a non‐native cysteine residue strategically placed around the hydrophobic tunnel of the protein. The three modified photoenzymes were shown to be selective for the oxidation of organic sulfides giving up to 192 turnovers.

Elemental Doping Boosts Charge-Transfer Excitonic States in Polymeric Photocatalysts for Selective Oxidation Reaction

Energy-transfer-mediated synthetic reactions play vital roles in the production of high-value-added organics, where the long-lived exciton harvesting is an essential precondition for the process. However, for semiconductors with strong excitonic effects like conjugated polymers, their predominant Frenkel exciton with a short lifetime in the unified framework gives rise to low efficiency photocatalysis. Herein, we propose the boosting of the charge-transfer exciton with a long-lived state by introducing spatially separated electron and hole regions. By taking polymeric carbon nitride (PCN) as a prototype, we demonstrate that sulfur doping leads to the formation of electron donor and acceptor motifs in the tri-s-triazine-based backbone, which would accommodate long-lived excitonic states with remarkable charge-transfer characteristics. The extraordinary long-lived charge-transfer exciton harvesting endows sulfur-doped PCN with high-efficiency photocatalytic performance in 1O2 generation and selective oxidation of organic sulfides. This work provides a brand new perspective for designing advanced photocatalysts for energy-transfer-mediated sunlight utilization.

The synergy between a benzoselenadiazole covalent organic framework and TEMPO for selective photocatalytic aerobic oxidation of organic sulfides

A benzoselenadiazole covalent organic framework works in synergy with TEMPO for selective photocatalysis in aerobic oxidation of organic sulfides.

Cooperative photocatalysis of dye-Ti-MCM-41 with trimethylamine for selective aerobic oxidation of sulfides illuminated by blue light.

Ti-incorporated mesoporous materials have widespread applications in photocatalysis. Their adjustable pores could accommodate dyes like alizarin red S (ARS) to circumvent the lack of visible light response. Herein, Ti-MCM-41 was obtained to anchor visible light-capturing ARS, forming ARS-Ti-MCM-41. The ARS-Ti-MCM-41 was screened for the selective photocatalytic oxidation of organic sulfides. To improve the stability of the anchored ARS, electron transfer was orchestrated by a mediator trimethylamine (TMA, 2mol%) illuminated by blue LEDs. Phenyl methyl sulfide could be almost entirely converted into phenyl methyl sulfoxide with 99% of selectivity within 18min. In addition, Ti-MCM-41 was beneficial for the anchored ARS, which in turn guaranteed good recycling performance of ARS-Ti-MCM-41. The solvent trifluoroethanol enabled the stability of TMA and facilitated the highly selective formation of the target sulfoxides. This work sheds light on the vast possibility for visible light photocatalysis of dye-mesoporous materials.

Fabrication of dianthracene-based hyper-cross-linked polymers for selective photocatalytic oxidation of organic sulfides

Two dianthracene-based hyper-cross-linked polymers are developed as photocatalysts for selective photocatalytic oxidation of organic sulfides for the first time.

2D β-ketoenamine-linked triazine covalent organic framework photocatalysis for selective oxidation of sulfides

Blue light-powered aerobic oxidation of organic sulfides sufficiently yields sulfoxides over TpTAPT-COF.

Inserting acetylene into an olefin-linked covalent organic framework for boosting the selective photocatalytic aerobic oxidation of sulfides

Covalent organic frameworks (COFs) with superior semiconducting properties imparted by sufficient π-conjugations and ordered structures have great potential in visible light photocatalysis. Thus, introducing extra π-conjugated rigid units into the olefin-linked COFs is effective to promote charge transfer and performance. Here, two olefin-linked COFs, TBP-COF and TBPA-COF, were synthesized by reacting 2,4,6-trimethyl-1,3,5-triazine (TMT) with 4,4′-bis(formyl)biphenyl (BFP) and bis(4-formylphenyl)acetylene (BFPA) through organic acid-induced solvothermal condensation. Both TBP-COF and TBPA-COF microspheres were with high crystallinity and uniform micropores. Owing to the insertion of acetylene, TBPA-COF possessed an extended π-conjugated structure that is conducive to smooth charge transfer. Compared to TBP-COF, TBPA-COF delivered superior photocatalytic performance on the selective aerobic oxidation of organic sulfides. Besides, both electron and energy transfer pathways contributed to the formation of sulfoxides over TBPA-COF. This work presents the ascendancy of inserting acetylene into olefin-linked COFs in building efficient visible light photocatalysts for organic oxidations.