REQUIMTE/LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal.
Víctor K. Abdelkader, Diana M. Fernandes, Salete S. Balula, Luis Cunha-Silva, Cristina Freire.
1 WHY PRODUCE POM@MOF COMPOSITES? Fe-MIL-101-NH2 Metal Organic Framework (MOF) MIL-101 structure - High specific areas - Large cage/pores sizes
Fe-containing - abundant cheap metal - significant catalytic activity1
2
NH2-containing - ↑ of POM-MOF interaction - N source for eventual carbonization/doping.
PREPARATION ‘IN SITU’ MOF synthesis in presence of POMs
1) ‘In situ’ POM@MOF synthesis, growing Fe-MIL-101-NH2 in presence of two different POMs, has been carried out.
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Iron salt MOF precursors
4 STRUCTURE
Samples Fe-MIL101-NH2 Cr-MIL -101-NH2
POM Preparation (TBA)3[PMo12O40] IN SITU (TBA)3[PMo11VO40] (TBA)3[PMo12O40] Impregnation (TBA)3[PMo11VO40]
CONCLUSIONS & OUTLOOK
POM@MOF composite
Organic ligand
MOF
4) Electron transfer numbers points out a 2-electron ORR pathway, with significant 2) Structural analysis HO2- production. demonstrate homogenous 5) ORR in immobilization of acid medium, as POM into the well as, other MOF’s structures. electrocatalytic processes will 3) Preliminary be studied. tests in ORR process have been performed.
Polyatomic anions consisting of 3 or more transition metal atoms linked together by O atoms, exhibiting attractive electrocatalytic properties.2
Solvothermal synthesis DMF, 110 °C, 24 h
+
Promising combination of POM and MOF features for application in (electro / heterogeneous) catalysis, sensors, etc.
Polyoxometalates (POMs)
POM
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e-mail:
[email protected]
Composite PMo12@MOF(Fe) PMo11V@MOF(Fe) PMo12@MOF(Cr) (*) PMo11V@MOF(Cr) (*)
IR spectra
5 ELECTROCHEMISTRY CV plots
LSV plots
(scan rate = 5 mV·s-1)
(scan rate = 5 mV·s-1, 1600 rpm)
(*) POM@MOF composites prepared via impregnation of Cr-MIL-101-NH2 with the corresponding POM (MeCN, stirring, 72 h) for comparative purposes.
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CHARACTERIZATION Structural characterization. Powder X-ray diffraction (PXRD) - Infrared spectroscopy (ATR). Electrochemical characterization. Oxygen Reduction Reaction (ORR) in alkaline medium (KOH(aq) 0.1 M) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV).
HO2- conversion: from LSV plots (scan rate = 5 mV·s-1, 1600 rpm) registered with double Ptring modified GC-disk electrode)
XRD patterns
REFERENCES
Electrochemical data Composite PMo12@MOF(Fe) PMo11V@MOF(Fe) PMo12@MOF(Cr) PMo11V@MOF(Cr)
1. a) Li X.; Tjiptoputro A. K.; Ding J.; Xue J. M.; Zhu Y. Catal. Today 2017, 279, 77. b) Wang D.; Li Z. Catal. Sci. Technol. 2015, 5, 1623. 2. a) Fernandes D. M.; Freire C. Chem. Electro. Chem. 2015, 2, 269. b) Lefebvre, F. Inorganics 2016, 4, 13.
While PMo12@MOF(Fe) composite exhibits the highest electron transfer number, PMo11V@MOF(Fe) reaches the highest percentage of hydrogen peroxide conversion.
No diffraction peaks assignable to POM present in the XRD patterns of composites → Homogenous distribution of POM anions in MOFs.
Characteristic vibrational bands of POM appear in the IR spectra of composites → POM successfully incorporated to POMs@MOFs.
n(a) 3.3 2.3 2.2 2.1
Eonset(b) (V) 0.64 0.65 0.65 0.64
HO2- (%) 58.8 70.7 51.0 23.2
(a) Electron transfer number per O2 determined from K-L plots (0.2 - 0.5 V). (b) Overpotential measured at the current density (j) of -0.1 mA·cm-2.
ACKNOWLEDGEMENTS The work was funded by Fundação para a Ciência e a Tecnologia (FCT)/MEC under FEDER under Program PT2020 - project UID/QUI/50006/2013-POCI/01/0145/FEDER/007265 and project “UniRCell”, with the reference POCI-01-0145-FEDER-016422
