TY - JOUR
T1 - Insights into the electrochemical behaviour of composite materials
T2 - Monovacant polyoxometalates @ porous metal-organic framework
AU - Videira, Patrícia de Mira Paes de Sousa
AU - Grazina, Raquel
AU - Barbosa, Andre D. S.
AU - de Castro, Baltazar
AU - Moura, José João Galhardas de
AU - Cunha-Silva, Luis
AU - Balula, Salete S.
N1 - Sem PDF.
Thanks are due to Fundacao para a Ciencia e a Tecnologia (FCT, MEC, Portugal) for financial support through the strategic project Pest-C/EQB/LA0006/2011 (to Associated Laboratory REQUIMTE), the R&D project PTDC/CTM/100357/2008 (LC-S), the program Ciencia 2007 (PMPS), and the post-doctoral fellowship SFRH/BPD/14938/2004 (to RG).
PY - 2013/1/1
Y1 - 2013/1/1
N2 - The first electrochemical investigation of composites materials based in polyoxometalates (POMs) encapsulated in the porous Metal-Organic Framework (MOE) MIL-101 is reported. The electrochemical behaviour of the porous MIL-101 and composite materials based in two monovacant Keggin-type POMs \{K-7{[}PW11O39]center dot 10H(2)O (PW11) and K-8{[}SiW11O39]center dot 13H(2)O (SiW11)\} encapsulated in MIL-101 (respectively, PW11@MIL-101 and SiW11@MIL-101) were studied by cyclic voltammetry. Initially, to investigate the influence of the support MIL-101 in the electrochemical behaviour of the two monovacant POMs, the compounds were individually immobilized on the surface of a pyrolytic graphite (PG) electrode. A reversible surface-controlled redox signal attributed to the chromium metal centres (Cr3+/Cr2+) was identified in MIL-101, and this represents the first electrochemical study of this MOP material. The monovacant compounds PW11 and SiW11 also revealed surface-controlled processes corresponding to W-VI <-> W-V reductions. PW11 showed two reversible signals (involving one or two electrons), whereas SiW11 showed a quasi-reversible one-electron and a reversible two-electron process for the first and second W reductions, respectively. For the latter, an extra process was detected and attributed to the formation of beta-isomer (beta-SiW11). When the composites materials PW11@MIL-101 and SiW11@MIL-101 were immobilized on the surface of the electrode, the support MIL-101 maintained its characteristic electrochemistry and the redox potentials of the POMs were not significantly changed. However, when encapsulated inside the cages of the support material the POMs revealed a distinct electrochemical behaviour, given that their redox processes became diffusion-controlled, indicating that the POMs have some degree of mobility inside the support framework.
AB - The first electrochemical investigation of composites materials based in polyoxometalates (POMs) encapsulated in the porous Metal-Organic Framework (MOE) MIL-101 is reported. The electrochemical behaviour of the porous MIL-101 and composite materials based in two monovacant Keggin-type POMs \{K-7{[}PW11O39]center dot 10H(2)O (PW11) and K-8{[}SiW11O39]center dot 13H(2)O (SiW11)\} encapsulated in MIL-101 (respectively, PW11@MIL-101 and SiW11@MIL-101) were studied by cyclic voltammetry. Initially, to investigate the influence of the support MIL-101 in the electrochemical behaviour of the two monovacant POMs, the compounds were individually immobilized on the surface of a pyrolytic graphite (PG) electrode. A reversible surface-controlled redox signal attributed to the chromium metal centres (Cr3+/Cr2+) was identified in MIL-101, and this represents the first electrochemical study of this MOP material. The monovacant compounds PW11 and SiW11 also revealed surface-controlled processes corresponding to W-VI <-> W-V reductions. PW11 showed two reversible signals (involving one or two electrons), whereas SiW11 showed a quasi-reversible one-electron and a reversible two-electron process for the first and second W reductions, respectively. For the latter, an extra process was detected and attributed to the formation of beta-isomer (beta-SiW11). When the composites materials PW11@MIL-101 and SiW11@MIL-101 were immobilized on the surface of the electrode, the support MIL-101 maintained its characteristic electrochemistry and the redox potentials of the POMs were not significantly changed. However, when encapsulated inside the cages of the support material the POMs revealed a distinct electrochemical behaviour, given that their redox processes became diffusion-controlled, indicating that the POMs have some degree of mobility inside the support framework.
KW - Electrochemistry
KW - Metal-organic framework
KW - Monovacant polyoxometalates
KW - MIL-101
KW - Electrochemistry
KW - Metal-organic framework
KW - MIL-101
KW - Monovacant polyoxometalates
U2 - 10.1016/j.electacta.2012.09.099
DO - 10.1016/j.electacta.2012.09.099
M3 - Article
SN - 0013-4686
VL - 87
SP - 853
EP - 859
JO - Electrochimica Acta
JF - Electrochimica Acta
ER -