Metal-zeolite catalysts promoting low-temperature methane oxidation to oxygenates

Abstract

Catalytic conversion of methane (CH₄) into value-added chemicals provides a viable path to reduce dependency on crude oil. Despite the challenges associated with activating methane’s C–H bond and limiting side reactions, low-temperature oxidation of methane to oxygenates has emerged as a promising approach, often hailed as a “grail reaction”. Zeolite-based metal (metal-zeolite) catalysts facilitate methane oxidation at low temperatures, converting methane into oxygenates while minimizing the complete oxidation to carbon dioxide (CO₂). This review highlights recent achievements in metal-zeolite catalysts for methane partial and coupling oxidation. With zeolite as the core, we explore the synthesis methods, metallic active sites, reaction mechanisms, and zeolite descriptors of metal-zeolite catalysts for methane partial oxidation. Additionally, we examine the critical role of mono- and bi-metallic species in metal-zeolite catalysts for methane coupling oxidation with carbon monoxide (CO). Finally, we discuss the challenges and opportunities for metal-zeolite catalysts in methane oxidation under mild conditions, proposing future directions for rational design of metal-zeolite catalysts, revealing reaction mechanisms through operando or in situ techniques, and leveraging artificial intelligence (AI) for enhanced catalytic efficiency.

Keywords

Metal-zeolite catalysts / low-temperature oxidation / methane conversion / oxygenated products

References

[1] Liu B,Chen H.The effect of oxidation of ethane to oxygenates on Pt- and Zn-containing LTA zeolites with tunable selectivity.J Energy Chem2019;30:42-8

[2] Armstrong R,Taylor S.An overview of recent advances of the catalytic selective oxidation of ethane to oxygenates.Catalysts2016;6:71

[3] Hammond C,Hermans I.Oxidative methane upgrading.ChemSusChem2012;5:1668-86

[4] Golisz SR,Goddard WA,Periana RA.Chemistry in the center for catalytic hydrocarbon functionalization: an energy frontier research center.Catal Lett2011;141:213-21

[5] Dinh KT,Serna P,Dincă M.Viewpoint on the partial oxidation of methane to methanol using Cu- and Fe-exchanged zeolites.ACS Catal2018;8:8306-13

[6] Heyer AJ,Braun A.Methane activation by a mononuclear copper active site in the zeolite mordenite: effect of metal nuclearity on reactivity.J Am Chem Soc2022;144:19305-16 PMCID:PMC9761895

[7] Forde MM,Hammond C.Partial oxidation of ethane to oxygenates using Fe- and Cu-containing ZSM-5.J Am Chem Soc2013;135:11087-99

[8] Wang C,Qin G.Direct conversion of syngas to ethanol within zeolite crystals.Chem2020;6:646-57

[9] Wang C,Wang L.Structure-performance interplay of rhodium-based catalysts for syngas conversion to ethanol.Mater Chem Front2022;6:663-79

[10] Pakhare D.A review of dry (CO₂) reforming of methane over noble metal catalysts.Chem Soc Rev2014;43:7813-37

[11] Movasati A,Mazloom G.Dry reforming of methane over CeO₂-ZnAl₂O₄ supported Ni and Ni-Co nano-catalysts.Fuel2019;236:1254-62

[12] Zhang Q,Corma A.Applications of zeolites to C1 chemistry: recent advances, challenges, and opportunities.Adv Mater2020;32:e2002927

[13] Taylor SH,Hutchings GJ,Lembacher CW.The partial oxidation of methane to methanol: an approach to catalyst design.Catal Today1998;42:217-24

[14] Ito T.Synthesis of ethylene and ethane by partial oxidation of methane over lithium-doped magnesium oxide.Nature1985;314:721-2

[15] Periana RA,Evitt ER.A mercury-catalyzed, high-yield system for the oxidation of methane to methanol.Science1993;259:340-3

[16] Periana RA,Gamble S,Satoh T.Platinum catalysts for the high-yield oxidation of methane to a methanol derivative.Science1998;280:560-4

[17] Mironov OA,Konnick MM.Using reduced catalysts for oxidation reactions: mechanistic studies of the “Periana-Catalytica” system for CH₄ oxidation.J Am Chem Soc2013;135:14644-58

[18] Baek J,Pei X.Bioinspired metal-organic framework catalysts for selective methane oxidation to methanol.J Am Chem Soc2018;140:18208-16

[19] Wang Q.State of the art and prospects in metal-organic framework (MOF)-based and MOF-derived nanocatalysis.Chem Rev2020;120:1438-511

[20] Ravi M,van Bokhoven JA.The direct catalytic oxidation of methane to methanol-A critical assessment.Angew Chem Int Ed Engl2017;56:16464-83

[21] Sushkevich VL,Ranocchiari M.Selective anaerobic oxidation of methane enables direct synthesis of methanol.Science2017;356:523-7

[22] Olivos-Suarez AI,Hensen EJM,Pidko EA.Strategies for the direct catalytic valorization of methane using heterogeneous catalysis: challenges and opportunities.ACS Catal2016;6:2965-81

[23] Wu L,Wang X.Methane oxidation over the zeolites-based catalysts.Catalysts2023;13:604

[24] Database of zeolite structures. http://www.iza-structure.org/databases/ (accessed 2025-02-10).

[25] Zhang Q,Yu J.Metal sites in zeolites: synthesis, characterization, and catalysis.Chem Rev2023;123:6039-106

[26] Li Y.New stories of zeolite structures: their descriptions, determinations, predictions, and evaluations.Chem Rev2014;114:7268-316

[27] Zhang Q,Terasaki O.Amino acid-assisted construction of single-crystalline hierarchical nanozeolites via oriented-aggregation and intraparticle ripening.J Am Chem Soc2019;141:3772-6

[28] Del Campo, P.; Martínez, C.; Corma, A. Activation and conversion of alkanes in the confined space of zeolite-type materials.Chem Soc Rev2021;50:8511-95

[29] Qi G,Nasrallah A.Au-ZSM-5 catalyses the selective oxidation of CH₄ to CH₃OH and CH₃COOH using O₂.Nat Catal2022;5:45-54

[30] Lewis RJ,Agarwal N,Morgan DJ.The direct synthesis of H₂O₂ and selective oxidation of methane to methanol using HZSM-5 supported AuPd catalysts.Catal Lett2019;149:3066-75

[31] Jin Z,Zuidema E.Hydrophobic zeolite modification for in situ peroxide formation in methane oxidation to methanol.Science2020;367:193-7

[32] Cao J,Yao B.Partially bonded aluminum site on the external surface of post-treated Au/ZSM-5 enhances methane oxidation to oxygenates.ACS Catal2024;14:1797-807

[33] Wang A,Zhang T.Heterogeneous single-atom catalysis.Nat Rev Chem2018;2:65-81

[34] Yuan J,Li X.A high performance catalyst for methane conversion to methanol: graphene supported single atom Co.Chem Commun2018;54:2284-7

[35] Lou Y,Hu W.Identification of active area as active center for CO oxidation over single Au atom catalyst.ACS Catal2020;10:6094-101

[36] Lou Y,Hu W.Low-temperature methane combustion over Pd/H-ZSM-5: active Pd sites with specific electronic properties modulated by acidic sites of H-ZSM-5.ACS Catal2016;6:8127-39

[37] Cui X,Wang Y.Room-temperature methane conversion by graphene-confined single iron atoms.Chem2018;4:1902-10

[38] Shan J,Allard LF,Flytzani-Stephanopoulos M.Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts.Nature2017;551:605-8

[39] Huang W,Tang Y.Low-temperature transformation of methane to methanol on Pd₁O₄ single sites anchored on the internal surface of microporous silicate.Angew Chem Int Ed Engl2016;55:13441-5]

[40] Kwon Y,Kwon G,Lee H.Selective activation of methane on single-atom catalyst of rhodium dispersed on zirconia for direct conversion.J Am Chem Soc2017;139:17694-9

[41] Shen Q,Huang R.Single chromium atoms supported on titanium dioxide nanoparticles for synergic catalytic methane conversion under mild conditions.Angew Chem Int Ed Engl2020;59:1216-9

[42] Gesser HD,Prakash CB.The direct conversion of methane to methanol by controlled oxidation.Chem Rev1985;85:235-44

[43] Mahyuddin MH,Yoshizawa K.Methane selective oxidation to methanol by metal-exchanged zeolites: a review of active sites and their reactivity.Catal Sci Technol2019;9:1744-68

[44] Kulkarni AR,Siahrostami S,Studt F.Cation-exchanged zeolites for the selective oxidation of methane to methanol.Catal Sci Technol2018;8:114-23

[45] Gunsalus NJ,Park SH,Hashiguchi BG.Homogeneous functionalization of methane.Chem Rev2017;117:8521-73

[46] Schwach P,Bao X.Direct conversion of methane to value-added chemicals over heterogeneous catalysts: challenges and prospects.Chem Rev2017;117:8497-520

[47] Zakaria Z.Direct conversion technologies of methane to methanol: an overview.Renew Sustain Energy Rev2016;65:250-61

[48] Panov GI,Rodkin MA.Generation of active oxygen species on solid surfaces. opportunity for novel oxidation technologies over zeolites.Catal Today1998;41:365-85

[49] Knops-Gerrits P.Methane partial oxidation in iron zeolites: theory versus experiment.J Mol Catal A Chem2001;166:135-45

[50] Wood B.Methanol formation on Fe/Al-MFI via the oxidation of methane by nitrous oxide.J Catal2004;225:300-6

[51] Dubkov K,Talsi E.Kinetic isotope effects and mechanism of biomimetic oxidation of methane and benzene on FeZSM-5 zeolite.J Mol Catal A Chem1997;123:155-61

[52] Groothaert MH,Sels BF,Schoonheydt RA.Selective oxidation of methane by the bis(mu-oxo)dicopper core stabilized on ZSM-5 and mordenite zeolites.J Am Chem Soc2005;127:1394-5

[53] Beznis NV,Weckhuysen BM.Oxidation of methane to methanol and formaldehyde over Co–ZSM-5 molecular sieves: tuning the reactivity and selectivity by alkaline and acid treatments of the zeolite ZSM-5 agglomerates.Micropor Mesopor Mat2011;138:176-83

[54] Bozbag SE,Pecháček J,Ranocchiari M.Methane to methanol over copper mordenite: yield improvement through multiple cycles and different synthesis techniques.Catal Sci Technol2016;6:5011-22

[55] Tomkins P,van Bokhoven JA.Direct conversion of methane to methanol under mild conditions over Cu-zeolites and beyond.Acc Chem Res2017;50:418-25

[56] Mlekodaj K,Kornas A.Evolution of active oxygen species originating from O₂ cleavage over Fe-FER for application in methane oxidation.ACS Catal2023;13:3345-55

[57] Beznis NV,Bitter JH.Partial oxidation of methane over Co-ZSM-5: tuning the oxygenate selectivity by altering the preparation route.Catal Lett2010;136:52-6

[58] Shan J,Nguyen L.Conversion of methane to methanol with a bent mono(μ-oxo)dinickel anchored on the internal surfaces of micropores.Langmuir2014;30:8558-69

[59] Xu J,Wang X.Room temperature activation of methane over Zn modified H-ZSM-5 zeolites: insight from solid-state NMR and theoretical calculations.Chem Sci2012;3:2932

[60] Hammond C,Lopez-Sanchez JA.Aqueous-phase methane oxidation over Fe-MFI zeolites; promotion through isomorphous framework substitution.ACS Catal2013;3:1835-44

[61] Sobolev V,Panna O.Selective oxidation of methane to methanol on a FeZSM-5 surface.Catal Today1995;24:251-2

[62] Lipscomb JD.Biochemistry of the soluble methane monooxygenase.Annu Rev Microbiol1994;48:371-99

[63] Chan SI,Yu SS,Kuo SS.Toward delineating the structure and function of the particulate methane monooxygenase from methanotrophic bacteria.Biochemistry2004;43:4421-30

[64] Lieberman RL.Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane.Nature2005;434:177-82

[65] Lieberman RL,Doan PE,Stemmler TL.Purified particulate methane monooxygenase from Methylococcus capsulatus (Bath) is a dimer with both mononuclear copper and a copper-containing cluster.Proc Natl Acad Sci U S A2003;100:3820-5 PMCID:PMC153005

[66] Yoshizawa K.Conversion of methane to methanol at the mononuclear and dinuclear copper sites of particulate methane monooxygenase (pMMO): a DFT and QM/MM study.J Am Chem Soc2006;128:9873-81

[67] Yoshizawa K.Nonradical mechanism for methane hydroxylation by iron-oxo complexes.Acc Chem Res2006;39:375-82

[68] Solomon EI,Johnston EM.Copper active sites in biology.Chem Rev2014;114:3659-853 PMCID:PMC4040215

[69] Pannov G,Kharitonov A.The role of iron in N₂O decomposition on ZSM-5 zeolite and reactivity of the surface oxygen formed.J Mol Catal1990;61:85-97

[70] Yoshizawa K,Yumura T.Direct methane−methanol and benzene−phenol conversions on Fe−ZSM-5 zeolite:  theoretical predictions on the reaction pathways and energetics.J Phys Chem B2000;104:734-40

[71] Groothaert MH,Battiston AA,Schoonheydt RA.Bis(mu-oxo)dicopper in Cu-ZSM-5 and its role in the decomposition of NO: a combined in situ XAFS, UV-vis-near-IR, and kinetic study.J Am Chem Soc2003;125:7629-40

[72] Smeets PJ,Woertink JS.Oxygen precursor to the reactive intermediate in methanol synthesis by Cu-ZSM-5.J Am Chem Soc2010;132:14736-8 PMCID:PMC2974621

[73] Tsai ML,Vanelderen P,Schoonheydt RA.[Cu₂O]²⁺ active site formation in Cu-ZSM-5: geometric and electronic structure requirements for N₂O activation.J Am Chem Soc2014;136:3522-9

[74] Beznis NV,Bitter JH.Cu-ZSM-5 zeolites for the formation of methanol from methane and oxygen: probing the active sites and spectator species.Catal Lett2010;138:14-22

[75] Woertink JS,Groothaert MH.A [Cu₂O]²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol.Proc Natl Acad Sci U S A2009;106:18908-13 PMCID:PMC2776445

[76] Forde MM,Mcvicker R.Light alkane oxidation using catalysts prepared by chemical vapour impregnation: tuning alcohol selectivity through catalyst pre-treatment.Chem Sci2014;5:3603-16

[77] Hammond C,Ab Rahim MH.Direct catalytic conversion of methane to methanol in an aqueous medium by using copper-promoted Fe-ZSM-5.Angew Chem Int Ed Engl2012;51:5129-33

[78] Fang Z,Zhao Q.Selective mild oxidation of methane to methanol or formic acid on Fe–MOR catalysts.Catal Sci Technol2019;9:6946-56

[79] Yu T,Wang A,Luo W.Efficient synthesis of monomeric Fe species in zeolite ZSM-5 for the low-temperature oxidation of methane.ChemCatChem2021;13:2766-70

[80] Kim MS,Cho SJ.Partial oxidation of methane with hydrogen peroxide over Fe-ZSM-5 catalyst.Catal Today2021;376:113-8

[81] Cheng Q,Yao X.Maximizing active Fe species in ZSM-5 zeolite using organic-template-free synthesis for efficient selective methane oxidation.J Am Chem Soc2023;145:5888-98 PMCID:PMC10021013

[82] Zhang Q,He G.Regulating mono-/binuclear Fe species in framework Al-rich zeolites for efficient low-temperature alkane oxidation. CCS. Chem. 2024.

[83] Shahami M.Zeolite acidity strongly influences hydrogen peroxide activation and oxygenate selectivity in the partial oxidation of methane over M,Fe-MFI (M: Ga, Al, B) zeolites.Catal Sci Technol2019;9:2945-51

[84] Oda A,Murata N.Rational design of ZSM-5 zeolite containing a high concentration of single Fe sites capable of catalyzing the partial oxidation of methane with high turnover frequency.Catal Sci Technol2022;12:542-50

[85] Yu T,Lin L.Highly selective oxidation of methane into methanol over Cu-promoted monomeric Fe/ZSM-5.ACS Catal2021;11:6684-91

[86] Kim MS,Park ED.Effects of Cu species on liquid-phase partial oxidation of methane with H₂O₂ over Cu-Fe/ZSM-5 catalysts.Catalysts2022;12:1224

[87] Göltl F,Andrikopoulos PC.Computationally exploring confinement effects in the methane-to-methanol conversion over iron-oxo centers in zeolites.ACS Catal2016;6:8404-9

[88] Mahyuddin MH,Shiota Y,Yoshizawa K.Roles of zeolite confinement and Cu–O–Cu angle on the direct conversion of methane to methanol by [Cu₂(μ-O)]²⁺ -exchanged AEI, CHA, AFX, and MFI zeolites.ACS Catal2017;7:3741-51

[89] Haw JF,Marcus DM.The mechanism of methanol to hydrocarbon catalysis.Acc Chem Res2003;36:317-26

[90] Snyder BER,Rhoda HM.Mechanism of selective benzene hydroxylation catalyzed by iron-containing zeolites.Proc Natl Acad Sci U S A2018;115:12124-9 PMCID:PMC6275498

[91] Snyder BER,Rhoda HM.Cage effects control the mechanism of methane hydroxylation in zeolites.Science2021;373:327-31 PMCID:PMC10353845

[92] Zhu K,Cui X.Highly efficient conversion of methane to formic acid under mild conditions at ZSM-5-confined Fe-sites.Nano Energy2021;82:105718

[93] Zheng J,Ortuño MA.Selective methane oxidation to methanol on Cu-oxo dimers stabilized by zirconia nodes of an NU-1000 metal-organic framework.J Am Chem Soc2019;141:9292-304

[94] Liu C,Yu SS.Heterogeneous formulation of the tricopper complex for efficient catalytic conversion of methane into methanol at ambient temperature and pressure.Energy Environ Sci2016;9:1361-74

[95] Hammond C,Jenkins RL.Elucidation and evolution of the active component within Cu/Fe/ZSM-5 for catalytic methane oxidation: from synthesis to catalysis.ACS Catal2013;3:689-99

[96] Szécsényi Á,Gascon J.Mechanistic complexity of methane oxidation with H₂O₂ by single-site Fe/ZSM-5 catalyst.ACS Catal2018;8:7961-72 PMCID:PMC6135593

[97] Kalamaras C,Bos R,Crimmin M.Selective oxidation of methane to methanol over Cu- and Fe-exchanged zeolites: the effect of Si/Al molar ratio.Catal Lett2016;146:483-92

[98] Yu T,Jones W.Identifying key mononuclear Fe species for low-temperature methane oxidation.Chem Sci2021;12:3152-60 PMCID:PMC8179404

[99] Zhang Q,Li L.Zeolite-based materials for greenhouse gas capture and conversion. Sci. China. Chem. 2024.

[100] Jia J,Wen B,Sachtler WMH.Identification of highly active iron sites in N₂O-activated Fe/MFI.Catal Lett2002;82:7-11

[101] Chow YK,Carter JH.Investigating the influence of acid sites in continuous methane oxidation with N₂O over Fe/MFI zeolites.Catal Sci Technol2018;8:154-63

[102] Xiao P,Lu Y.One-pot synthesized Fe-AEI zeolite catalysts contribute to direct oxidation of methane.ACS Catal2023;13:16168-78

[103] Xiao P,Toyoda H.Revealing active sites and reaction pathways in direct oxidation of methane over Fe-containing CHA zeolites affected by the Al arrangement.J Am Chem Soc2024;146:31969-81

[104] Zhu L,Liu B.Ozone-assisted low-temperature oxidation of methane and ethane.P Combust Inst2023;39:375-84

[105] Ipek B.Catalytic conversion of methane to methanol on Cu-SSZ-13 using N₂O as oxidant.Chem Commun2016;52:13401-4

[106] Tsuchimura Y,Machida M,Takahashi K.Investigation of the active-site structure of Cu-CHA catalysts for the direct oxidation of methane to methanol using in situ UV-vis spectroscopy.Energy Fuels2023;37:9411-8

[107] Bols ML,Rhoda HM.Selective formation of α-Fe(II) sites on Fe-zeolites through one-pot synthesis.J Am Chem Soc2021;143:16243-55

[108] Plessers D,Rhoda HM.Tuning copper active site composition in Cu-MOR through Co-cation modification for methane activation.ACS Catal2023;13:1906-15 PMCID:PMC10299574

[109] Jeong YR,Kang J,Park ED.Continuous synthesis of methanol from methane and steam over copper-mordenite.ACS Catal2021;11:1065-70

[110] Xiao P,Lu Y.Effects of Al distribution in the Cu-exchanged AEI zeolites on the reaction performance of continuous direct conversion of methane to methanol.Appl Catal B Environ2023;325:122395

[111] Artsiusheuski MA,Sushkevich VL.Structure of selective and nonselective dicopper (II) sites in CuMFI for methane oxidation to methanol.ACS Catal2022;12:15626-37

[112] Xiao P,Nakamura K.Highly effective Cu/AEI zeolite catalysts contribute to continuous conversion of methane to methanol.ACS Catal2023;13:11057-68

[113] Brezicki G,Gunnoe TB,Davis RJ.Insights into the speciation of Cu in the Cu-H-mordenite catalyst for the oxidation of methane to methanol.ACS Catal2019;9:5308-19

[114] Kucherov AV,Kucherova TN.Stabilization of the ethane oxidation catalytic activity of Cu-ZSM-5.Appl Catal B Environ1996;7:285-98

[115] Vanelderen P,Smeets PJ,Schoonheydt RA.Cu-ZSM-5: a biomimetic inorganic model for methane oxidation.J Catal2011;284:157-64 PMCID:PMC3593946

[116] Alayon EM,Ranocchiari M.Catalytic conversion of methane to methanol using Cu-zeolites.Chimia2012;66:668-74

[117] Dinh KT,Narsimhan K.Continuous partial oxidation of methane to methanol catalyzed by diffusion-paired copper dimers in copper-exchanged zeolites.J Am Chem Soc2019;141:11641-50

[118] Narsimhan K,Dinh K.Catalytic oxidation of methane into methanol over copper-exchanged zeolites with oxygen at low temperature.ACS Cent Sci2016;2:424-9 PMCID:PMC4919767

[119] Sushkevich VL.Effect of Brønsted acid sites on the direct conversion of methane into methanol over copper-exchanged mordenite.Catal Sci Technol2018;8:4141-50

[120] Smeets PJ,Schoonheydt RA.Cu based zeolites: a UV-vis study of the active site in the selective methane oxidation at low temperatures.Catal Today2005;110:303-9

[121] Artsiusheuski MA,Palagin D,Sushkevich VL.Structural evolution of copper-oxo sites in zeolites upon the reaction with methane investigated by means of Cu K-edge X-ray absorption spectroscopy.J Phys Chem C2023;127:9603-15

[122] Lee I,Tao L.Activity of Cu-Al-oxo extra-framework clusters for selective methane oxidation on Cu-exchanged zeolites.JACS Au2021;1:1412-21 PMCID:PMC8479761

[123] Khramenkova EV,Li G.Unraveling the nature of extraframework catalytic ensembles in zeolites: flexibility and dynamics of the copper-oxo trimers in mordenite.J Phys Chem Lett2021;12:10906-13 PMCID:PMC8591661

[124] Xiao P,Wang L.Understanding the effect of spatially separated Cu and acid sites in zeolite catalysts on oxidation of methane.Nat Commun2024;15:2718 PMCID:PMC10978981

[125] Wijerathne A,Daya R.Competition between mononuclear and binuclear copper sites across different zeolite topologies.JACS Au2024;4:197-215 PMCID:PMC10806779

[126] Wang Y,Chen M.Low-silica Cu-CHA zeolite enriched with Al pairs transcribed from silicoaluminophosphate seed: synthesis and ammonia selective catalytic reduction performance.Angew Chem Int Ed Engl2023;62:e202306174

[127] Brezicki G,Paolucci C,Davis RJ.Effect of the Co-cation on Cu speciation in Cu-exchanged mordenite and ZSM-5 catalysts for the oxidation of methane to methanol.ACS Catal2021;11:4973-87

[128] Gabrienko AA,Kolganov AA.Methane activation on H-ZSM-5 zeolite with low copper loading. the nature of active sites and intermediates identified with the combination of spectroscopic methods.Inorg Chem2020;59:2037-50

[129] Ohyama J,Hirayama A.Relationships among the catalytic performance, redox activity, and structure of Cu-CHA catalysts for the direct oxidation of methane to methanol investigated using in situ XAFS and UV-vis spectroscopies.ACS Catal2022;12:2454-62

[130] Göltl F,Lebrón-Rodríguez EA.Identifying hydroxylated copper dimers in SSZ-13 via UV-vis-NIR spectroscopy.Catal Sci Technol2022;12:2744-8

[131] Li H,Khurana I.Consequences of exchange-site heterogeneity and dynamics on the UV-visible spectrum of Cu-exchanged SSZ-13.Chem Sci2019;10:2373-84 PMCID:PMC6385673

[132] Rhoda HM,Heyer AJ.Spectroscopic definition of a highly reactive site in Cu-CHA for selective methane oxidation: tuning a mono-μ-oxo dicopper(II) active site for reactivity.J Am Chem Soc2021;143:7531-40

[133] Zhang Y,Wang H.Selective catalytic reduction of NO_x with NH₃ over Cu/SSZ-13: elucidating dynamics of Cu active sites with in situ UV-vis spectroscopy and DFT calculations.J Phys Chem C2022;126:8720-33

[134] Tang X,Yang B.Direct oxidation of methane to oxygenates on supported single Cu atom catalyst.Appl Catal B Environ2021;285:119827

[135] Heyer AJ,Ma J.Magnetic exchange coupling in zeolite copper dimers and its contribution to methane activation.J Am Chem Soc2024;146:6061-71 PMCID:PMC11285328

[136] Li G,Sanchez-Sanchez M,Hensen EJ.Stability and reactivity of copper oxo-clusters in ZSM-5 zeolite for selective methane oxidation to methanol.J Catal2016;338:305-12

[137] Armstrong RD,Ritterskamp N,Taylor SH.The role of copper speciation in the low temperature oxidative upgrading of short chain alkanes over Cu/ZSM-5 catalysts.Chemphyschem2018;19:469-78

[138] Grundner S,Li G.Single-site trinuclear copper oxygen clusters in mordenite for selective conversion of methane to methanol.Nat Commun2015;6:7546 PMCID:PMC4491810

[139] Yuan Q,Zhang Q.Osmium-catalyzed selective oxidations of methane and ethane with hydrogen peroxide in aqueous medium.Adv Synth Catal2007;349:1199-209

[140] Kulkarni AR,Siahrostami S,Studt F.Monocopper active site for partial methane oxidation in Cu-exchanged 8MR zeolites.ACS Catal2016;6:6531-6

[141] Sushkevich VL,Klose D,van Bokhoven JA.Identification of kinetic and spectroscopic signatures of copper sites for direct oxidation of methane to methanol.Angew Chem Int Ed Engl2021;60:15944-53

[142] Mahyuddin MH,Shiota Y.Direct conversion of methane to methanol by metal-exchanged ZSM-5 zeolite (metal = Fe, Co, Ni, Cu).ACS Catal2016;6:8321-31

[143] Pierella LB,Caglieri SC,Bercoff PG.Catalytic activity and magnetic properties of Co–ZSM-5 zeolites prepared by different methods.Appl Catal A Gen2008;347:55-61

[144] Mahyuddin MH,Kitagawa R.Distinct behaviors of Cu- and Ni-ZSM-5 zeolites toward the post-activation reactions of methane.J Phys Chem C2021;125:19333-44

[145] Mahyuddin MH.DFT exploration of active site motifs in methane hydroxylation by Ni-ZSM-5 zeolite.Catal Sci Technol2018;8:5875-85

[146] Xiao P,Lu Y.Direct oxidation of methane to methanol over transition-metal-free ferrierite zeolite catalysts.J Am Chem Soc2024;146:10014-22 PMCID:PMC11009945

[147] Wang L,Zhu Y.Catalysis and in situ studies of Rh₁/Co₃O₄ nanorods in reduction of NO with H₂.ACS Catal2013;3:1011-9

[148] Nguyen L,Wang L.Reduction of nitric oxide with hydrogen on catalysts of singly dispersed bimetallic sites Pt₁Co_m and Pd₁Co_n.ACS Catal2016;6:840-50

[149] Zhang S,Liang JX.Catalysis on singly dispersed bimetallic sites.Nat Commun2015;6:7938

[150] Bai S,Huang B.High-efficiency direct methane conversion to oxygenates on a cerium dioxide nanowires supported rhodium single-atom catalyst.Nat Commun2020;11:954 PMCID:PMC7031227

[151] Zhu J,Ishikawa R.Ultrafast encapsulation of metal nanoclusters into MFI zeolite in the course of its crystallization: catalytic application for propane dehydrogenation.Angew Chem Int Ed Engl2020;59:19669-74

[152] Tao FF,Nguyen L.Understanding complete oxidation of methane on spinel oxides at a molecular level.Nat Commun2015;6:7798

[153] Guo X,Li G.Direct, nonoxidative conversion of methane to ethylene, aromatics, and hydrogen.Science2014;344:616-9

[154] Bai S,Xu Y,Huang X.Strong synergy in a lichen-like RuCu nanosheet boosts the direct methane oxidation to methanol.Nano Energy2020;71:104566

[155] Ab Rahim MH,Hammond C.Systematic study of the oxidation of methane using supported gold palladium nanoparticles under mild aqueous conditions.Top Catal2013;56:1843-57

[156] Bai S,Wang P,Huang X.Activating and converting CH₄ to CH₃OH via the CuPdO₂/CuO nanointerface.ACS Catal2019;9:6938-44

[157] Plauck A,Dumesic JA.Active sites and mechanisms for H₂O₂ decomposition over Pd catalysts.Proc Natl Acad Sci U S A2016;113:E1973-82 PMCID:PMC4833276

[158] Flaherty DW.Direct synthesis of H₂O₂ from H₂ and O₂ on Pd catalysts: current understanding, outstanding questions, and research needs.ACS Catal2018;8:1520-7

[159] Agarwal N,McVicker RU.Aqueous Au-Pd colloids catalyze selective CH₄ oxidation to CH₃OH with O₂ under mild conditions.Science2017;358:223-7

[160] Williams C,Dummer NF.Selective oxidation of methane to methanol using supported AuPd catalysts prepared by stabilizer-free sol-immobilization.ACS Catal2018;8:2567-76

[161] He Y,Imai Y.Highly selective synthesis of methanol from methane over carbon materials supported Pd-Au nanoparticles under mild conditions.Catal Today2020;352:104-10

[162] Freakley SJ,van Marwijk J.A chemo-enzymatic oxidation cascade to activate C-H bonds with in situ generated H₂O₂.Nat Commun2019;10:4178 PMCID:PMC6744418

[163] Crombie CM,Taylor RL.Enhanced selective oxidation of benzyl alcohol via in situ H₂O₂ production over supported Pd-based catalysts.ACS Catal2021;11:2701-14

[164] Ab Rahim MH,Jenkins RL.Oxidation of methane to methanol with hydrogen peroxide using supported gold-palladium alloy nanoparticles.Angew Chem Int Ed Engl2013;52:1280-4

[165] Wu B,Huang M.Tandem catalysis for selective oxidation of methane to oxygenates using oxygen over PdCu/zeolite.Angew Chem Int Ed Engl2022;61:e202204116

[166] Cheng Q,Li G.Atomically dispersed iron-copper dual-metal sites synergistically boost carbonylation of methane.Angew Chem Int Ed Engl2024;63:e202411048

[167] Moteki T,Ogura M.Mechanism investigation and product selectivity control on CO-assisted direct conversion of methane into C1 and C2 oxygenates catalyzed by zeolite-supported Rh.Appl Catal B Environ2022;300:120742

[168] Narsimhan K,Mathies G,Griffin RG.Methane to acetic acid over Cu-exchanged zeolites: mechanistic insights from a site-specific carbonylation reaction.J Am Chem Soc2015;137:1825-32 PMCID:PMC5412725

[169] Wang X,Xu J,Wang C.NMR-spectroscopic evidence of intermediate-dependent pathways for acetic acid formation from methane and carbon monoxide over a ZnZSM-5 zeolite catalyst.Angew Chem Int Ed Engl2012;51:3850-3

[170] Blasco T,Concepción P,Law D.Carbonylation of methanol on metal-acid zeolites: evidence for a mechanism involving a multisite active center.Angew Chem Int Ed Engl2007;46:3938-41

[171] Boronat M,Law D.Enzyme-like specificity in zeolites: a unique site position in mordenite for selective carbonylation of methanol and dimethyl ether with CO.J Am Chem Soc2008;130:16316-23

[172] Moteki T,Ogura M.CO-assisted direct methane conversion into C₁ and C₂ oxygenates over ZSM-5 supported transition and platinum group metal catalysts using oxygen as an oxidant.ChemCatChem2020;12:2957-61

[173] Wang C,Wang L.Oxidative carbonylation of methane to acetic acid on an Fe-modified ZSM-5 zeolite.Appl Catal B Environ2023;329:122549

[174] Tang Y,Fung V.Single rhodium atoms anchored in micropores for efficient transformation of methane under mild conditions.Nat Commun2018;9:1231 PMCID:PMC5964318

[175] Cao J,Qi G.Methane conversion to methanol using Au/ZSM-5 is promoted by carbon.ACS Catal2023;13:7199-209

[176] Wu B,Ma X.Highly selective synthesis of acetic acid from hydroxyl-mediated oxidation of methane at low temperatures.Angew Chem Int Ed Engl2025;64:e202412995