Heterogeneous formulation of the tricopper complex for efficient catalytic conversion of methane into methanol at ambient temperature and pressure

Liu, Chih‐Cheng; Mou, Chung‐Yuan; Yu, Steve S.‐F.; Chan, Sunney I.

doi:10.1039/c5ee03372a

Cited by 71 publications

(86 citation statements)

References 50 publications

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“…Model compounds provide an excellent foundation for eventual interpretation of spectroscopic features of pMMO reaction intermediates, but it should be noted that no isolated dicopper complex has been shown to oxidize methane. Methane to methanol conversion by tricopper complexes and zeolites containing tricopper species has also been reported [152–156]. However, no copper has been observed at the site of the proposed PmoA tricopper active site [116, 117], and the exact electronic structure of the species giving rise to an EPR signal assigned to a tricopper site [116, 124, 125] remains unclear [106, 157–159].…”

Section: Possible O2 Activation Intermediatesmentioning

confidence: 99%

A tale of two methane monooxygenases

Ross¹,

2016

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Methane monooxygenase (MMO) enzymes activate O2 for oxidation of methane. Two distinct MMOs exist in nature, a soluble form that uses a diiron active site (sMMO) and a membrane-bound form with a catalytic copper center (pMMO). Understanding the reaction mechanisms of these enzymes is of fundamental importance to biologists and chemists, and is also relevant to the development of new biocatalysts. The sMMO catalytic cycle has been elucidated in detail, including O2 activation intermediates and the nature of the methane-oxidizing species. By contrast, many aspects of pMMO catalysis remain unclear, most notably the nuclearity and molecular details of the copper active site. Here, we review the current state of knowledge for both enzymes, and consider pMMO O2 activation intermediates suggested by computational and synthetic studies in the context of existing biochemical data. Further work is needed on all fronts, with the ultimate goal of understanding how these two remarkable enzymes catalyze a reaction not readily achieved by any other metalloenzyme or biomimetic compound.

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Section: Possible O2 Activation Intermediatesmentioning

confidence: 99%

A tale of two methane monooxygenases

Ross¹,

2016

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“…1000 times higher than that of natural HRP and 100 times highert han those of most HRP mimics based on metal/metal oxide NPsreported to date. [186] Immobilization of at ricopper complex [Cu I Cu I Cu I (7-N-Etppz)] + (CuEtp;7 -N-Etppz = 3,30-(1,4-diazepane-1,4-diyl)bis[1-(4-ethyl-piperazine-1-yl)propan-2-ol]) ( Figure 21) on mesoporous silica nanoparticles also resulted in significant improvement of the catalytic activity and TONs with higher chemical yields, offering the most proficient catalyst for the selective conversion of methane into methanola tr oom temperature, [187] as compared with other heterogeneous catalysts. [188][189][190][191][192][193][194][195][196] When [Cu I Cu I Cu I (7-N-Etppz)] + was employed as ah omogeneous catalyst for oxidation of methanew ith 20 equiv of H 2 O 2 at room temperature, the maximum TON was only 6.5.…”

Section: Enhanced Redox Catalysismentioning

confidence: 99%

Immobilization of Molecular Catalysts for Enhanced Redox Catalysis

2018

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In the homogenous phase, redox catalysts are often deactivated by bimolecular reactions. For example, the charge‐separated state of photoredox catalysts decayed via bimolecular back electron transfer reactions between the charge‐separated molecules to decrease the lifetimes of the catalytically active species. When photoredox catalysts are immobilized on solid supports, the lifetime of the charge‐separated state was remarkably elongated to enhance the photocatalytic activity. Immobilization of photoredox catalysts on electrodes is required for photocurrent generation, leading to development of solar cells. Metal‐oxygen intermediates, which are active for oxidation of various substrates including water oxidation, are also deactivated via bimolecular reactions to produce inactive forms such as dinuclear metal bis‐μ‐oxo complexes. Immobilization of metal complex catalysts on solid supports prohibits the bimolecular deactivation, enhancing the catalytic activity and stability. This Review focuses on recent development of immobilization of both organic and inorganic molecular catalysts on various supports for enhancement of the catalytic activity, selectivity and stability in thermal and photoinduced redox reactions.

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“…Recently, trinuclear Cu clusters formed with a trinucleating ligand were reported by the Chan group to effect catalytic hydroxylation of hydrocarbon substrates including methane, using O 2 and a sacrificial reductant. More productive hydroxylation reactivity is found using H 2 O 2 as the oxidant in both homogeneous and heterogenized solutions [95,96]. The active oxidant is proposed as a localized valence Cu(III)Cu(II)Cu(II) mono-oxide cluster, as opposed to the μ 2 -oxide of the T clusters.…”

Section: Monooxygenase Reactivity Of O Speciesmentioning

confidence: 99%

High-valent copper in biomimetic and biological oxidations

2016

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A long-standing debate in the Cu-O2 field has revolved around the relevance of the Cu(III) oxidation state in biological redox processes. The proposal of Cu(III) in biology is generally challenged as no spectroscopic or structural evidence exists currently for its presence. The reaction of synthetic Cu(I) complexes with O2 at low temperature in aprotic solvents provides the opportunity to investigate and define the chemical landscape of Cu-O2 species at a small molecule level of detail; eight different types are characterized structurally, three of which contain at least one Cu(III) center. Simple imidazole or histamine ligands are competent in these oxygenation reactions to form Cu(III) complexes. The combination of synthetic structural and reactivity data suggests (i) that Cu(I) should be considered as either a one or two electron reductant reacting with O2, (ii) that Cu(III) reduction potentials of these formed complexes are modest and well within the limits of a protein matrix and (iii) that primary amine and imidazole ligands are surprisingly good at stabilizing Cu(III) centers. These Cu(III) complexes are efficient oxidants for hydroxylating phenolate substrates with reaction hallmarks similar to that performed in biological systems. The remarkable ligation similarity of the synthetic and biological systems makes it difficult to continue to exclude Cu(III) from biological discussions.

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Heterogeneous formulation of the tricopper complex for efficient catalytic conversion of methane into methanol at ambient temperature and pressure

Abstract: The development of a heterogeneous catalyst capable for efficient selective conversion of methane into methanol with multiple turnovers under ambient conditions is reported here.

Cited by 71 publications

References 50 publications

A tale of two methane monooxygenases

A tale of two methane monooxygenases

Immobilization of Molecular Catalysts for Enhanced Redox Catalysis

High-valent copper in biomimetic and biological oxidations

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