Selective Methane Oxidation by Heterogenized Iridium Catalysts

Li, Haoyi; Fei, Muchun; Troiano, Jennifer L.; Ma, Lu; Yan, Xingxu; Tieu, Peter; Yuan, Yucheng; Zhang, Yuhan; Liu, Tianying; Pan, Xiaoqing; Brudvig, Gary W.; Wang, Dunwei

doi:10.1021/jacs.2c09434

Cited by 15 publications

(8 citation statements)

References 37 publications

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“…Since their discovery, cyclometalated iridium complexes have been extensively studied in various applications, such as biological probes, , photosensitizers, , catalysts, , and sensors. , The use of Ir(III) complexes as emitters in organic light-emitting diodes (OLEDs) is their most widely developed application. − Due to the strong spin–orbit coupling (SOC) induced by the heavy metal, iridium(III) complexes have relatively short excited state lifetimes among phosphorescent compounds and therefore are suitable for OLED applications. , Phosphorescent iridium complexes can often have near-unity quantum yields − in the green and yellow regions, and thus OLED devices with colors in these regions are very efficient and represent a low research priority in the display industry.…”

Section: Introductionmentioning

confidence: 99%

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Modular Imine Chelates with Variable Anionic Donors Promote Red Phosphorescence in Cyclometalated Iridium Complexes

et al. 2023

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The lack of red and deep-red emitting molecular phosphors with high photoluminescence quantum yields remains a significant fundamental challenge and has implications in optoelectronic technologies for color displays and other consumer products. In this work, we introduce a series of seven new red or deep-red emitting heteroleptic bis-cyclometalated iridium(III) complexes, supported by five different ancillary ligands (L^X) from the salicylaldimine and 2-picolinamide families. Previous work had shown that electron-rich anionic chelating “L^X” ligands can be effective in supporting efficient red phosphorescence, and the complementary approach described here, in addition to being synthetically simpler, offers two key advantages over the previous designs. First, the “L” and “X” functionalities can be independently tuned, providing excellent control over the electronic energy levels and excited-state dynamics. Second, these classes of L^X ligands can have beneficial impacts on the excited-state dynamics but do not significantly perturb the emission color profile. Cyclic voltammetry experiments show that the substituents on the L^X ligand impact the HOMO energy but have a minimal effect on the LUMO energy. Photoluminescence measurements reveal that all the compounds luminesce in the red or deep-red region as a function of the cyclometalating ligand and exhibit exceptionally high photoluminescence quantum yields (ΦPL), comparable or superior to the best-performing red-emitting iridium complexes.

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Section: Introductionmentioning

confidence: 99%

“…Since their discovery, cyclometalated iridium complexes have been extensively studied in various applications, such as biological probes, 1,2 photosensitizers, 3,4 catalysts, 5,6 and sensors. 7,8 The use of Ir(III) complexes as emitters in organic light-emitting diodes (OLEDs) is their most widely developed application.…”

Section: ■ Introductionmentioning

confidence: 99%

Modular Imine Chelates with Variable Anionic Donors Promote Red Phosphorescence in Cyclometalated Iridium Complexes

et al. 2023

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“…As a promising feedstock of chemicals and liquid fuels, methane has attracted much attention due to its high reserve and cheap supply. Direct oxidation of methane into value-added oxygenates under mild conditions becomes an ideal transformation route, − but it remains a challenge because activation of the strong C–H bond of methane (bond energy = 104 kcal/mol) is difficult. In recent years, relatively strong oxidants of sulfur trioxide and hydrogen peroxide were used to oxidize methane into value-added oxygenates under mild conditions. ,− For example, sulfur trioxide was used to prepare methanesulfonic acid from methane, and excellent activity was reached at 50 °C .…”

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confidence: 99%

Acid-Promoted Selective Oxidation of Methane to Formic Acid over Dispersed Rhodium Catalysts under Mild Conditions

Qin

Pang

et al. 2023

ACS Catal.

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Direct oxidation of methane into value-added liquid chemicals is a promising route for wide applications. However, the efficient conversion of methane with high selectivity under mild conditions is still challenging. Herein, the catalysts of rhodium dispersed on ZSM-5 were synthesized for the methane conversion utilizing molecular O2 as the oxidant together with CO and H2O under a total pressure of 40 bar at <100 °C. Moreover, the conversion of methane and the selectivity of formic acid could be improved by increasing acidity over the Rh/ZSM-5 catalysts. Promoted by H+, the activities of methane oxidation can reach 3.56 molHCOOH/molRh/h and 23.96 molHCOOH/molRh/h at 50 and 90 °C over the 5.0Rh/H-ZSM-5 catalyst, and the selectivity of HCOOH of 98.48% to all organic oxygenates can be acquired at 90 °C. Dramatically, the activation of the C–H bond can even happen at room temperature. Electron paramagnetic resonance results showed that acidity can promote the generation of ·OH with CO, H2O, and O2 as the reactants, resulting in high catalytic activity under mild conditions.

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“…Direct conversion of methane (CH 4 ) into methanol (CH 3 OH) provides a feasible route for efficient energy storage and the production of valuable chemicals. − Over the past century, the scientific challenge for this dream reaction is the prevention of CH 3 OH overoxidation, which is often more reactive than CH 4 conversion. − To achieve high selectivity, in most cases harsh operation conditions − (high pressure and strongly acidic media) and overpriced oxidants − are crucial for selective oxidation of CH 4 to CH 3 OH, which feature serious challenges for environmental and economic sustainability. Taking hydrogen peroxide (H 2 O 2 ; one of the most common-used oxidants) as an example, its cost is even higher than the generated CH 3 OH. − Under such circumstances, it is highly demanded to find alternative routes that circumvent the difficulty of using expensive oxidants and achieve highly selective oxidation of CH 4 to CH 3 OH under moderate conditions.…”

Section: Introductionmentioning

confidence: 99%

Selective Cleavage of Chemical Bonds in Targeted Intermediates for Highly Selective Photooxidation of Methane to Methanol

et al. 2023

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Restrained by the uncontrollable cleavage process of chemical bonds in methane molecules and corresponding formed intermediates, the target product in the reaction of methane selective oxidation to methanol would suffer from an inevitable overoxidation process, which is considered to be one of the most challenging issues in the field of catalysis. Herein, we report a conceptually different method for modulating the conversion pathway of methane through the selective cleavage of chemical bonds in the key intermediates to suppress the generation of peroxidation products. Taking metal oxides, typical semiconductors in the field of methane oxidation as model catalysts, we confirm that the cleavage of different chemical bonds in CH 3 O* intermediates could greatly affect the conversion pathway of methane, which has a vital role in product selectivity. Specifically, it is revealed that the formation of peroxidation products could be significantly prevented by the selective cleavage of C−O bonds in CH 3 O* intermediates instead of metal−O bonds, which is proved by the combination of density functional theory calculations and in situ infrared spectroscopy based on isotope labeling. By manipulating the lattice oxygen mobility of metal oxides, the electrons transferring from the surface to the CH 3 O* intermediates could directionally inject into the antibonding orbitals of the C−O bond, resulting in its selective cleavage. As a result, the gallium oxide with low lattice oxygen mobility shows a 3.8% conversion rate for methane with a high methanol generation rate (∼325.4 μmol g −1 h −1 ) and selectivity (∼87.0%) under room temperature and atmospheric pressure in the absence of extra oxidants, which is superior among the reported studies (reaction pressure: <20 bar).

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Selective Methane Oxidation by Heterogenized Iridium Catalysts

Cited by 15 publications

References 37 publications

Modular Imine Chelates with Variable Anionic Donors Promote Red Phosphorescence in Cyclometalated Iridium Complexes

Modular Imine Chelates with Variable Anionic Donors Promote Red Phosphorescence in Cyclometalated Iridium Complexes

Acid-Promoted Selective Oxidation of Methane to Formic Acid over Dispersed Rhodium Catalysts under Mild Conditions

Selective Cleavage of Chemical Bonds in Targeted Intermediates for Highly Selective Photooxidation of Methane to Methanol

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