Analysis of electrocatalytic metal-organic frameworks

Abstract

The electrochemical analysis of molecular catalysts for the conversion of bulk feedstocks into energy-rich clean fuels has seen dramatic advances in the last decade. More recently, increased attention has focused on the characterization of metal-organic frameworks (MOFs) containing well-defined redox and catalytically active sites, with the overall goal to develop structurally stable materials that are industrially relevant for large-scale solar fuel syntheses. Successful electrochemical analysis of such materials draws heavily on well-established homogeneous techniques, yet the nature of solid materials presents additional challenges. In this tutorial-style review, we cover the basics of electrochemical analysis of electroactive MOFs, including considerations of bulk stability, methods of attaching MOFs to electrodes, interpreting fundamental electrochemical data, and finally electrocatalytic kinetic characterization. We conclude with a perspective of some of the prospects and challenges in the field of electrocatalytic MOFs.

Diagnosing surface versus bulk reactivity for molecular catalysis within metal–organic frameworks using a quantitative kinetic model

“…denitions of TOF need to be adopted, 4,19 the apparent turnover frequency (TOF app ) and the true turnover frequency (TOF true ):…”

“…This is advantageous as it can stabilize the molecular catalyst and avoid undesired bimolecular decomposition reactions, while providing a heterogeneous support matrix with a high density of anchoring sites. MOF-supported molecular catalysis has been previously demonstrated for energy related processes [3][4][5][6] including proton reduction, 7-9 CO 2 reduction, [10][11][12][13][14] and water oxidation, [15][16][17][18][19][20] as well as a variety of organic transformations with high-value products. [21][22][23][24][25] However, given the interfacial nature of the reactions occurring in MOFs, mass and charge transport by a diffusional process are required to shuttle reactants, substrates, as well as electrons or holes to the molecular active sites in the MOF interior.…”

Synthetic strategies to incorporate Ru-terpyridyl water oxidation catalysts into MOFs: direct synthesis vs. post-synthetic approach

“…A high catalyst loading is desirable as it gives rise to the least possible distance between redox active metallolinkers which would facilitate charge hopping through the framework. 5,16 Traditionally, DMF is used as the solvent in solvothermal synthesis of UiO-type MOFs. However, DMF is known to coordinate to the ruthenium centre and deactivate the catalyst.…”

“…Such a strategy makes the complex an integral part of the framework without occupying the void of the MOF that provides for ion, substrate and product transport. 5 In the present work, we seek to develop a reliable synthetic approach to Ru(tda)-MOF composite materials using Ru(tda) (PyCO 2 H) 2 (PyCO 2 H = iso-nicotinic acid, Fig. 1B), modified with axial carboxylates, as metallo-linker.…”

Enhancing Photovoltages at p-Type Semiconductors Through a Redox-active Metal-Organic Framework Surface Coating

“…Nonetheless, simply increasing the number of sites may not always result in a current enhancement, as diffusional processes can become limiting as films become thicker. 40 To calculate the diffusion coefficient of the film, the chronoamperometry data was fitted to the Cottrell equation (eq. 1):…”