Exploring the impact of successive redox events in thin films of Metal-Organic Frameworks: an absorptiometric approach
Résumé
Metal-organic frameworks (MOFs) featuring redox activity are highly appealing for electrocatalytic or charge accumulation applications. An important aspect in this field is the ability to address as many redox centers as possible in the material by an efficient diffusion of charges. Herein, we investigate for the first time the charge diffusion processes occurring upon two sequential one-electron reductions in a MOF thin film. Two pyrazolate-zinc(II) based metal-organic frameworks (MOFs) including highly electro-deficient perylene diimide (PDI) ligands were grown on conducting substrates, affording thin films with double n-type electrochromic properties as characterized by spectroelectrochemical analysis. In depth electrochemical and chronoabsorptiometric investigations were carried out to probe the charge diffusion in the MOF layers and highlighted significant differences in terms of diffusion kinetics and material stability, between the first and second successive reduction of the redox active PDI linkers. Our results show that MOFs based on multi-redox centers are more sensitive to encumbrance-related issues than their mono-redox analogues in the context of electrochemical applications, an observation that further underlines the fundamental aspect of pore dimensions toward efficient and fast ion diffusion.
Mots clés
Metal-Organic Framework charge diffusion electrochromism electrochemistry MOF-modified electrodes fast diffusion perylene diimide pyrazolate ligand multi-redox processes
Metal-Organic Framework
charge diffusion
electrochromism
electrochemistry
MOF-modified electrodes
fast diffusion
perylene diimide
pyrazolate ligand
multi-redox processes
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