Name: Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks
Uploaded: 2023-06-09T14:10:00
Description: Watch this Scientific Journal Video about Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks at JoVE.com

Denne studien ble støttet av en Japan Society for the Promotion of Science (JSPS) KAKENHI Grant (JP20H05621). Z. Zhang takker også Tatematsu Foundation og Toyota Riken-stipendet for økonomisk støtte.

1. Elektrode fabrikasjon
<ol><li>Syntetisere Cu-THQ MOF MERK: Cu-THQ MOF polykrystallinsk pulver ble syntetisert via en hydrotermisk metode etter tidligere publiserte prosedyrer 14,20,23.<ol><li>Sett 60 mg tetrahydroksykinon i en 20 ml ampulle, tilsett deretter 10 ml avgasset vann. Oppløs 110 mg kobber (II) nitrattrihydrat i et separat hetteglass i ytterligere 10 ml avgasset vann. Tilsett 46 μL a...

Magnetometric Characterization of Redox-Active MOFs Solid-State Electrochemistry

<ol>
	<li>Lee, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-organic+framework+materials+as+catalysts.">Metal-organic framework materials as catalysts.</a> Chemical Society Reviews. 38 (5), 1450-1459 (2009).</li><li>Dolgopolova, E. A., Rice, A. M., Martin, C. R., Shustova, N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemistry+and+photophysics+of+MOFs:+steps+towards+MOF-based+sensing+enhancements.">Photochemistry and photophysics of MOFs: steps towards MOF-based sensing enhancements.</a> Chemical Society Reviews. 47 (13), 4710-4728 (2018).</li><li>Qian, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MOF-based+membranes+for+gas+separations.">MOF-based membranes for gas separations.</a> Chemical Reviews. 120 (16), 8161-8266 (2020).</li><li>Wang, Q., Astruc, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State+of+the+art+and+prospects+in+metal-organic+framework+(MOF)-based+and+MOF-derived+nanocatalysis.">State of the art and prospects in metal-organic framework (MOF)-based and MOF-derived nanocatalysis.</a> Chemical Reviews. 120 (2), 1438-1511 (2020).</li><li>Wang, M., Dong, R., Feng, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+conjugated+metal-organic+frameworks+(2D+c-MOFs):+chemistry+and+function+for+MOFtronics.">Two-dimensional conjugated metal-organic frameworks (2D c-MOFs): chemistry and function for MOFtronics.</a> Chemical Society Reviews. 50 (4), 2764-2793 (2021).</li><li>Baumann, A. E., Burns, D. A., Liu, B., Thoi, V. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-organic+framework+functionalization+and+design+strategies+for+advanced+electrochemical+energy+storage+devices.">Metal-organic framework functionalization and design strategies for advanced electrochemical energy storage devices.</a> Communications Chemistry. 2 (1), 86 (2019).</li><li>Nam, K. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conductive+2D+metal-organic+framework+for+high-performance+cathodes+in+aqueous+rechargeable+zinc+batteries.">Conductive 2D metal-organic framework for high-performance cathodes in aqueous rechargeable zinc batteries.</a> Nature Communications. 10 (1), 4948 (2019).</li><li>Sheberla, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conductive+MOF+electrodes+for+stable+supercapacitors+with+high+areal+capacitance.">Conductive MOF electrodes for stable supercapacitors with high areal capacitance.</a> Nature Materials. 16 (2), 220-224 (2017).</li><li>Wang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrathin+two-dimensional+conjugated+metal-organic+framework+single-crystalline+nanosheets+enabled+by+surfactant-assisted+synthesis.">Ultrathin two-dimensional conjugated metal-organic framework single-crystalline nanosheets enabled by surfactant-assisted synthesis.</a> Chemical Science. 11 (29), 7665-7671 (2020).</li><li>Zhang, Z., Yoshikawa, H., Awaga, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+the+solid-state+electrochemistry+of+Cu(2,7-AQDC)+(AQDC+=+anthraquinone+dicarboxylate)+in+a+lithium+battery:+Coexistence+of+metal+and+ligand+redox+activities+in+a+metal-organic+framework.">Monitoring the solid-state electrochemistry of Cu(2,7-AQDC) (AQDC = anthraquinone dicarboxylate) in a lithium battery: Coexistence of metal and ligand redox activities in a metal-organic framework.</a> Journal of the American Chemical Society. 136 (46), 16112-16115 (2014).</li><li>Zhang, Z., Yoshikawa, H., Awaga, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discovery+of+a+&amp;#34;bipolar+charging&amp;#34;+mechanism+in+the+solid-state+electrochemical+process+of+a+flexible+metal-organic+framework.">Discovery of a &amp;#34;bipolar charging&amp;#34; mechanism in the solid-state electrochemical process of a flexible metal-organic framework.</a> Chemistry of Materials. 28 (5), 1298-1303 (2016).</li><li>Li, C., Hu, X., Hu, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cobalt(II)+dicarboxylate-based+metal-organic+framework+for+long-cycling+and+high-rate+potassium-ion+battery+anode.">Cobalt(II) dicarboxylate-based metal-organic framework for long-cycling and high-rate potassium-ion battery anode.</a> Electrochimica Acta. 253, 439-444 (2017).</li><li>Liu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reversible+formation+of+coordination+bonds+in+Sn-based+metal-organic+frameworks+for+high-performance+lithium+storage.">Reversible formation of coordination bonds in Sn-based metal-organic frameworks for high-performance lithium storage.</a> Nature Communications. 12 (1), 3131 (2021).</li><li>Jiang, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+redox-active+2D+metal-organic+framework+for+efficient+lithium+storage+with+extraordinary+high+capacity.">A redox-active 2D metal-organic framework for efficient lithium storage with extraordinary high capacity.</a> Angewandte Chemie. 59 (13), 5273-5277 (2020).</li><li>Sakaushi, K., Nishihara, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+&#960;-conjugated+frameworks+as+a+model+system+to+unveil+a+multielectron-transfer-based+energy+storage+mechanism.">Two-dimensional &#960;-conjugated frameworks as a model system to unveil a multielectron-transfer-based energy storage mechanism.</a> Accounts of Chemical Research. 54 (15), 3003-3015 (2021).</li><li>Li, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2D+organic+radical+conjugated+skeletons+with+paramagnetic+behaviors.">2D organic radical conjugated skeletons with paramagnetic behaviors.</a> Advanced Materials Interfaces. 8 (18), 2100943 (2021).</li><li>Peeks, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electronic+delocalization+in+the+radical+cations+of+porphyrin+oligomer+molecular+wires.">Electronic delocalization in the radical cations of porphyrin oligomer molecular wires.</a> Journal of the American Chemical Society. 139 (30), 10461-10471 (2017).</li><li>Krug von Nidda, H. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anisotropic+exchange+in+LiCuVO4+probed+by+ESR.">Anisotropic exchange in LiCuVO4 probed by ESR.</a> Physical Review B. 65 (13), 134445 (2002).</li><li>Zeng, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pro-aromatic+and+anti-aromatic+&#960;-conjugated+molecules:+An+irresistible+wish+to+be+diradicals.">Pro-aromatic and anti-aromatic &#960;-conjugated molecules: An irresistible wish to be diradicals.</a> Chemical Society Reviews. 44 (18), 6578-6596 (2015).</li><li>Chen, Q., Adeniran, O., Liu, Z. F., Zhang, Z., Awaga, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphite-like+charge+storage+mechanism+in+a+2D+&#960;-d+conjugated+metal-organic+framework+revealed+by+stepwise+magnetic+monitoring.">Graphite-like charge storage mechanism in a 2D &#960;-d conjugated metal-organic framework revealed by stepwise magnetic monitoring.</a> Journal of the American Chemical Society. 145 (2), 1062-1071 (2023).</li><li>Julien, C. M., Mauger, A., Groult, H., Zhang, X., Gendron, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LiCo1-yByO2+as+cathode+materials+for+rechargeable+lithium+batteries.">LiCo1-yByO2 as cathode materials for rechargeable lithium batteries.</a> Chemistry of Materials. 23 (2), 208-218 (2011).</li><li>Niem&#246;ller, A., Jakes, P., Eichel, R. A., Granwehr, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+operando+EPR+investigation+of+redox+mechanisms+in+LiCoO2.">In operando EPR investigation of redox mechanisms in LiCoO2.</a> Chemical Physics Letters. 716, 231-236 (2019).</li><li>Park, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthetic+routes+for+a+2D+semiconductive+copper+hexahydroxybenzene+metal-organic+framework.">Synthetic routes for a 2D semiconductive copper hexahydroxybenzene metal-organic framework.</a> Journal of the American Chemical Society. 140 (44), 14533-14537 (2018).</li><li>Rondeau, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+technique+for+degassing+liquid+samples.">A technique for degassing liquid samples.</a> Journal of Chemical Education. 44 (9), 530 (1967).</li><li>Flores-Llamas, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhomogeneously+broadened+EPR+lineshape+of+axial+powder.">Inhomogeneously broadened EPR lineshape of axial powder.</a> Applied Magnetic Resonance. 9 (2), 289-298 (1995).</li><li>Sun, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room-temperature+quantitative+quantum+sensing+of+lithium+ions+with+a+radical-embedded+metal-organic+framework.">Room-temperature quantitative quantum sensing of lithium ions with a radical-embedded metal-organic framework.</a> Journal of the American Chemical Society. 144 (41), 19008-19016 (2022).</li><li>Chen, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Successive+storage+of+cations+and+anions+by+ligands+of+&#960;-d-conjugated+coordination+polymers+enabling+robust+sodium-ion+batteries.">Successive storage of cations and anions by ligands of &#960;-d-conjugated coordination polymers enabling robust sodium-ion batteries.</a> Angewandte Chemie. 60 (34), 18769-18776 (2021).</li><li>Roessler, M. M., Salvadori, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Principles+and+applications+of+EPR+spectroscopy+in+the+chemical+sciences.">Principles and applications of EPR spectroscopy in the chemical sciences.</a> Chemical Society Reviews. 47 (8), 2534-2553 (2018).</li><li>Ji, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pauli+paramagnetism+of+stable+analogues+of+pernigraniline+salt+featuring+ladder-type+constitution.">Pauli paramagnetism of stable analogues of pernigraniline salt featuring ladder-type constitution.</a> Journal of the American Chemical Society. 142 (1), 641-648 (2020).</li><li>Noel, M., Santhanam, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemistry+of+graphite+intercalation+compounds.">Electrochemistry of graphite intercalation compounds.</a> Journal of Power Sources. 72 (1), 53-65 (1998).</li><li>Wu, K. H., Ting, T. H., Wang, G. P., Ho, W. D., Shih, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+carbon+black+content+on+electrical+and+microwave+absorbing+properties+of+polyaniline/carbon+black+nanocomposites.">Effect of carbon black content on electrical and microwave absorbing properties of polyaniline/carbon black nanocomposites.</a> Polymer Degradation and Stability. 93 (2), 483-488 (2008).</li><li>Yao, M., Taguchi, N., Ando, H., Takeichi, N., Kiyobayashi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+gravimetric+energy+density+and+cycle+life+in+organic+lithium-ion+batteries+with+naphthazarin-based+electrode+materials.">Improved gravimetric energy density and cycle life in organic lithium-ion batteries with naphthazarin-based electrode materials.</a> Communications Materials. 1 (1), 70 (2020).</li><li>Krzystek, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EPR+spectra+from+&amp;#34;EPR-silent&amp;#34;+species:+High-frequency+and+high-field+EPR+spectroscopy+of+pseudotetrahedral+complexes+of+nickel(II).">EPR spectra from &amp;#34;EPR-silent&amp;#34; species: High-frequency and high-field EPR spectroscopy of pseudotetrahedral complexes of nickel(II).</a> Inorganic Chemistry. 41 (17), 4478-4487 (2002).</li></ol>

For å produsere katoder er det nødvendig å blande det aktive materialet med ledende karbon for å oppnå lav polarisering under den elektrokjemiske prosessen. Karbonadditivet er det første kritiske punktet for ex situ magnetometri; hvis karbonet har radikale defekter, kan fremveksten av det elektrokjemisk induserte organiske radikalet ikke observeres i ESR-spekteret. Dette gjør det vanskelig å nøyaktig bestemme spinnkonsentrasjonen eller organisk radikalkonsentrasjon, siden disse to typer radikaler har li...

Siden begrepet metallorganisk rammeverk (MOF) ble introdusert på slutten av 1990-tallet, og spesielt på 2010-tallet, har de mest representative vitenskapelige konseptene om MOFs oppstått fra deres strukturelle porøsitet, inkludert gjesteinnkapsling, separasjon, katalytiske egenskaper og molekyl sensing 1,2,3,4 . I mellomtiden var forskere raske til å innse at det er viktig for MOFs å ha stimuli-responsive elektroniske egenskaper for å integrere dem i moderne smarte enheter. Denne ideen utløste gyting og blomstring av den ledende todimensjonale (2D) MOF-familien de siste 10 årene, og åpnet dermed porten for MOF-er til å spille nøkkelroller i elektronikk5 og, mer attraktivt, i elektrokjemiske energilagringsenheter6. Disse 2D MOF-ene har blitt innlemmet som aktive materialer i alkalimetallbatterier, vandige batterier, pseudokondensatorer og superkondensatorer 7,8,9, og har vist enorm kapasitet og utmerket stabilitet. For å designe 2D MOF-er med bedre ytelse er det imidlertid avgjørende å forstå ladelagringsmekanismene deres i detalj. Derfor har denne artikkelen som mål å gi en omfattende forståelse av de elektrokjemiske mekanismene til MOF, som kan hjelpe til med den rasjonelle utformingen av bedre ytelse MOFs for energilagringsapplikasjoner.
I 2014 rapporterte vi først solid-state elektrokjemiske mekanismer av MOFs med redoks-aktive steder på både metallkationer og ligander10,11. Disse mekanismene ble tolket ved hjelp av ulike in situ og ex situ spektroskopiske teknikker, som røntgenfotoelektronspektroskopi (XPS), røntgenabsorpsjonsfinstruktur (XAFS), røntgendiffraksjon (XRD) og solid-state kjernemagnetisk resonans (NMR). Siden da har dette forskningsparadigmet blitt en trend i studier av faststoffelektrokjemi av molekylærbaserte materialer12. Disse metodene fungerer fint for å identifisere redokshendelsene til konvensjonelle MOFer med karboksylatbroligander, da molekylorbitaler og energinivåer av metallklyngebyggesteiner og organiske ligander er nesten uavhengige av hverandre i slike MOFer12,13.
Men når de møtte de sterkt korrelerte 2D MOFene med signifikant π-d konjugering, ble begrensningene til disse spektroskopiske metodene eksponert. En av disse begrensningene er at båndnivåene til de fleste nevnte 2D MOF-er ikke kan betraktes som en enkel kombinasjon av metallklynger og ligander, men snarere er en hybridisering av dem, mens de fleste spektroskopiske metoder bare gir gjennomsnittlig, kvalitativ informasjon om oksidasjonstilstandene14. Den andre begrensningen er at tolkningen av disse dataene alltid er basert på antagelsen om lokaliserte atomorbitaler. Derfor blir mellomtilstandene med metallligandhybridisering og delokaliserte elektroniske tilstander vanligvis oversett og beskrevet feil med bare disse spektroskopiske metodene15. Det er nødvendig å utvikle nye sonder for de elektroniske tilstandene til disse elektrokjemiske mellomproduktene av ikke bare 2D MOF, men også andre materialer med lignende konjugerte eller sterkt korrelerte elektroniske strukturer, slik som kovalente organiske rammer16, molekylære ledere og konjugerte polymerer17.
De vanligste og kraftigste verktøyene for å vurdere materialets elektroniske strukturer er elektronspinnresonans (ESR) og superledende kvanteinterferensenhet (SQUID) magnetiske følsomhetsmålinger18,19. Siden begge er avhengige av uparede elektroner i systemet, kan disse verktøyene gi tentativ informasjon om spinntettheter, spinnfordelinger og spinn-spinn-interaksjoner. ESR tilbyr sensitiv deteksjon av uparede elektroner, mens magnetisk følsomhetsmåling gir mer kvantitative signaler for øvre egenskaper20. Dessverre står begge teknikkene uunngåelig overfor store utfordringer når de brukes til å analysere de elektrokjemiske mellomproduktene. Dette skyldes at målprøver ikke er rene, men snarere en blanding av målmateriale, ledende additiv, bindemiddel og biprodukt fra elektrolytten, så de oppnådde dataene21,22 er summen av bidrag fra både materialet og urenhetene. I mellomtiden er de fleste mellomprodukter følsomme for miljøet, inkludert luft, vann, visse elektrolytter eller andre uforutsigbare forstyrrelser; Ekstra forsiktighet er nødvendig ved håndtering og måling av mellomprodukter. Prøving og feiling er normalt nødvendig når man arbeider med en ny kombinasjon av elektrodemateriale og elektrolytt.
Her presenterer vi et nytt paradigme, kalt elektrokjemisk magnetometri, for å analysere de elektroniske tilstandene eller spinntilstandene til 2D MOFs og lignende materialer ved hjelp av en rekke teknikker, ved hjelp av elektrokjemi og temperaturvariabel ex situ ESR-spektroskopi samt ex situ magnetiske følsomhetsmålinger20. For å demonstrere effektiviteten av denne tilnærmingen bruker vi Cu3THQ 2 (THQ = 1,2,4,5-tetrahydroxybenzoquinone; referert til som Cu-THQ), en representant2D MOF, som et eksempel. Vi forklarer valg av ledende tilsetningsstoffer og elektrolytter, fremstilling av elektroder og elektrokjemiske celler, samt detaljer om prøvehåndtering og måling, inkludert mulige problemer under måling. Ved å sammenligne med klassiske karakteriseringer som XRD og XAFS, kan elektrokjemisk magnetometri gi en omfattende forståelse av den elektrokjemiske mekanismen til de fleste MOFs. Denne tilnærmingen er i stand til å fange unike mellomtilstander og unngå feil tildeling av redokshendelser. Belysningen av energilagringsmekanismer ved hjelp av elektrokjemisk magnetometri kan også bidra til en bedre forståelse av struktur-funksjonsforholdene i MOFs, noe som fører til mer intelligente syntetiske strategier for MOFs og andre konjugerte materialer.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1-Methyl-2-pyrrolidone</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>139-17611</td>
			<td>Super Dehydrated</td>
		</tr>
		<tr>
			<td>1mol/L LiBF4 EC:DEC (1:1 v/v%)</td>
			<td>Kishida</td>
			<td>LBG-96533</td>
			<td>electrolyte</td>
		</tr>
		<tr>
			<td>4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>089-04191</td>
			<td>TEMPOL, for Spin Labeling&#160;</td>
		</tr>
		<tr>
			<td>Ampule tube</td>
			<td>Maruemu Corporation</td>
			<td>5-124-05</td>
			<td>20mL</td>
		</tr>
		<tr>
			<td>Carbon black, Super P Conductive</td>
			<td>Alfa Aesar</td>
			<td>H30253</td>
			<td></td>
		</tr>
		<tr>
			<td>Conductive Carbon Black</td>
			<td>Mitsubishi Chemical</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Copper (II) Nitrate Trihydrate</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>033-12502</td>
			<td>deleterious substances</td>
		</tr>
		<tr>
			<td>Dimethyl Carbonate</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>046-31935</td>
			<td>battery grade</td>
		</tr>
		<tr>
			<td>Ethylenediamine</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>053-00936</td>
			<td>deleterious substances</td>
		</tr>
		<tr>
			<td>Graphene Nanoplatelets</td>
			<td>Tokyo Chemical Industry</td>
			<td>G0442</td>
			<td>6-8nm(thick), 15&#181;m(wide)</td>
		</tr>
		<tr>
			<td>Poly(vinylidene fluoride)</td>
			<td>Sigma Aldrich</td>
			<td>182702</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Bromide</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>165-17111</td>
			<td>for Infrared Spectrophotometry</td>
		</tr>
		<tr>
			<td>Sodium Alginate&#160;</td>
			<td>FUJIFILM Wako Chemicals</td>
			<td>199-09961</td>
			<td>500-600 cP</td>
		</tr>
		<tr>
			<td>SQUID Magnetometer</td>
			<td>Quantum Design</td>
			<td>MPMS-XL 5</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydroxy-1,4-benzoquinone Hydrate</td>
			<td>Tokyo Chemical Industry</td>
			<td>T1090</td>
			<td></td>
		</tr>
		<tr>
			<td>X-Band ESR</td>
			<td>JEOL</td>
			<td>JES-F A200</td>
			<td></td>
		</tr>
	</tbody>
</table>

magnetometric characterization of intermediates in the solid-state electrochemistry of redox-active metal-organic frameworks

Elektrokjemisk energilagring har vært en mye diskutert anvendelse av redoksaktive metallorganiske rammer (MOF) de siste 5 årene. Selv om MOF-er viser fremragende ytelse når det gjelder gravimetrisk eller arealkapasitans og syklisk stabilitet, er deres elektrokjemiske mekanismer dessverre ikke godt forstått i de fleste tilfeller. Tradisjonelle spektroskopiske teknikker, som røntgenfotoelektronspektroskopi (XPS) og røntgenabsorpsjonsfinstruktur (XAFS), har bare gitt vag og kvalitativ informasjon om valensendringer av visse elementer, og mekanismene som foreslås basert på slik informasjon er ofte svært diskutable. I denne artikkelen rapporterer vi en rekke standardiserte metoder, inkludert fabrikasjon av elektrokjemiske celler i fast tilstand, elektrokjemiske målinger, demontering av celler, innsamling av MOF-elektrokjemiske mellomprodukter og fysiske målinger av mellomproduktene under beskyttelse av inerte gasser. Ved å bruke disse metodene for kvantitativt å avklare den elektroniske og spinntilstandsutviklingen innenfor et enkelt elektrokjemisk trinn av redoksaktive MOFer, kan man gi klar innsikt i naturen til elektrokjemiske energilagringsmekanismer, ikke bare for MOF, men også for alle andre materialer med sterkt korrelerte elektroniske strukturer.

Since the term metal-organic framework (MOF) was introduced in the late 1990s, and especially in the 2010s, the most representative scientific concepts concerning MOFs have arisen from their structural porosity, including guest encapsulation, separation, catalytic properties, and molecule sensing1,2,3,4. Meanwhile, scientists were quick to realize that it is essential for MOFs to possess stimuli-responsive electronic properties in order to integrate them into modern smart devices. This idea triggered the spawning and flourishing of the conductive two-dimensional (2D) MOF family in the past 10 years, thereby opening the gate for MOFs to play key roles in electronics5 and, more attractively, in electrochemical energy storage devices6. These 2D MOFs have been incorporated as active materials in alkali metal batteries, aqueous batteries, pseudocapacitors, and supercapacitors7,8,9, and have exhibited tremendous capacity as well as excellent stability. However, to design better-performing 2D MOFs, it is crucial to understand their charge storage mechanisms in detail. Therefore, this article aims to provide a comprehensive understanding of the electrochemical mechanisms of MOFs, which can aid in the rational design of better-performing MOFs for energy storage applications.
In 2014, we first reported the solid-state electrochemical mechanisms of MOFs with redox-active sites on both metal cations and ligands10,11.&#160;These mechanisms were interpreted with the help of various in situ and ex situ spectroscopic techniques, such as X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (NMR). Since then, this research paradigm has become a trend in studies of the solid-state electrochemistry of molecular-based materials12. These methods work fine for identifying the redox events of conventional MOFs with carboxylate bridging ligands, as the molecular orbitals and energy levels of metal cluster building blocks and organic ligands are almost independent of each other in such MOFs12,13.
However, when encountering the strongly correlated 2D MOFs with significant &#960;-d conjugation, the limitations of these spectroscopic methods were exposed. One of these limitations is that the band levels of most aforementioned 2D MOFs cannot be considered as a simple combination of metal clusters and ligands, but are rather a hybridization of them, while most of the spectroscopic methods only provide averaged, qualitative information about the oxidation states14. The other limitation is that the interpretation of these data is always based on the assumption of localized atomic orbitals. Therefore, the intermediate states with metal-ligand hybridization and delocalized electronic states are usually overlooked and described incorrectly with only these spectroscopic methods15. It is necessary to develop new probes for the electronic states of these electrochemical intermediates of not only 2D MOFs, but also other materials with similar conjugated or strongly correlated electronic structures, such as covalent organic frameworks16, molecular conductors, and conjugated polymers17.
The most common and powerful tools for assessing the electronic structures of materials are electron spin resonance (ESR) and superconducting quantum interference device (SQUID) magnetic susceptibility measurements18,19. As both rely on unpaired electrons in the system, these tools can provide tentative information about the spin densities, spin distributions, and spin-spin interactions. ESR offers sensitive detection of unpaired electrons, while magnetic susceptibility measurement gives more quantitative signals for upper properties20. Unfortunately, both techniques unavoidably face great challenges when used to analyze the electrochemical intermediates. This is because target samples are not pure, but rather a mixture of target material, conductive additive, binder, and byproduct from the electrolyte, so the obtained data21,22 are the sum of contributions from both the material and the impurities. Meanwhile, most intermediates are sensitive to the environment, including air, water, certain electrolytes, or any other unpredictable perturbations; extra care is necessary while handling and measuring intermediates. Trial and error is normally necessary while dealing with a new combination of electrode material and electrolyte.
Here, we present a new paradigm, called electrochemical magnetometry, for analyzing the electronic states or spin states of 2D MOFs and similar materials using a series of techniques, utilizing electrochemistry and temperature-variable ex situ ESR spectroscopy as well as ex situ magnetic susceptibility measurements20. To demonstrate the effectiveness of this approach, we use Cu3THQ2 (THQ = 1,2,4,5-tetrahydroxybenzoquinone; referred to as Cu-THQ), a representative 2D MOF, as an example. We explain the selection of conductive additives and electrolytes, the fabrication of electrodes and electrochemical cells, as well as details on sample handling and measurement, including possible issues during measurement. By comparing with classic characterizations such as XRD and XAFS, electrochemical magnetometry can provide a comprehensive understanding of the electrochemical mechanism of most MOFs. This approach is capable of capturing unique intermediate states and avoiding incorrect assignment of redox events. The elucidation of energy storage mechanisms using electrochemical magnetometry can also contribute to a better understanding of the structure-function relationships in MOFs, leading to more intelligent synthetic strategies for MOFs and other conjugated materials.

Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks  

Magnetometrisk karakterisering av mellomprodukter i faststoffelektrokjemi av redoks-aktive metallorganiske rammer

Our research interest lies in understanding the electronic and spin states of 2D pi-d conjugated metal organic frameworks and their correlation with their electrochemical behavior of this MOFs in solid-state energy storage devices. In the last five years, many new 2D-conjugating MOF materials have been reported and studied for their use as active materials in electrochemical cells. However, the mechanism of their charge storage processes is still unclear.Spectroscopic methods, including X-ray diffraction, X-ray photoelectron spectroscopy, and the X-ray absorption fine structure are the mostly common used techniques in this field. Those techniques are crucial for categorizing the specific element's crystal structure and oxygen states. It is not possible to separate a 2D MOF from the device while analyzing its electrochemical intermediate state.Measurement must be taken on a mixture that includes conductive additives and binders. However, to accurately determine the MOF's electrochemical behavior, it is necessary to calibrate the contribution of these additives. Most spectroscopic measures assume well localized electrons in MOFs, but our protocol provides a physical view and reveals strongly-correlated phenomena in these materials.We will continue to better understand the electronic, magnetic, and quantum properties of 2D-conjugated MOFs and bridge the gap between coordination chemistry and solid-state physics through physical insights.

Vårt tidligere arbeid inkluderte en detaljert diskusjon av ex situ ESR-spektroskopi og ex situ magnetiske følsomhetsmålinger for elektrokjemisk syklet CuTHQ20. Her presenterer vi de mest representative og detaljerte resultatene som kan oppnås ved å følge protokollen beskrevet i denne artikkelen.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65335/65335fig02.jpg"> Fig...

Watch this Scientific Journal Video about Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks at JoVE.com

Ex situ magnetiske undersøkelser kan direkte gi bulk og lokal informasjon på en magnetisk elektrode for å avsløre ladningslagringsmekanismen trinn for trinn. Her er elektronspinnresonans (ESR) og magnetisk følsomhet demonstrert for å overvåke evalueringen av paramagnetiske arter og deres konsentrasjon i et redoksaktivt metallorganisk rammeverk (MOF).

Electrochemical energy storage has been a widely discussed application of redox-active metal-organic frameworks (MOFs) in the past 5 years. Although MOFs ...

Vår forskningsinteresse ligger i å forstå de elektroniske og spinntilstandene til 2D pi-d konjugerte metallorganiske rammer og deres korrelasjon med deres elektrokjemiske oppførsel av disse MOF-ene i solid-state energilagringsenheter. I løpet av de siste fem årene har mange nye 2D-konjugerende MOF-materialer blitt rapportert og studert for bruk som aktive materialer i elektrokjemiske celler. Imidlertid er mekanismen for deres ladelagringsprosesser fortsatt uklar.Spektroskopiske metoder, inkludert røntgendiffraksjon, røntgenfotoelektronspektroskopi og røntgenabsorpsjonsfinstruktur er de vanligste teknikkene på dette feltet. Disse teknikkene er avgjørende for å kategorisere det spesifikke elementets krystallstruktur og oksygentilstander. Det er ikke mulig å skille en 2D MOF fra enheten mens du analyserer dens elektrokjemiske mellomtilstand.Måling må tas på en blanding som inneholder ledende tilsetningsstoffer og bindemidler. For å bestemme MOFs elektrokjemiske oppførsel nøyaktig, er det imidlertid nødvendig å kalibrere bidraget fra disse tilsetningsstoffene. De fleste spektroskopiske tiltak forutsetter godt lokaliserte elektroner i MOF, men vår protokoll gir et fysisk syn og avslører sterkt korrelerte fenomener i disse materialene.Vi vil fortsette å bedre forstå de elektroniske, magnetiske og kvanteegenskapene til 2D-konjugerte MOF-er og bygge bro over gapet mellom koordinasjonskjemi og faststofffysikk gjennom fysisk innsikt.