Molecular Catalysts that Oxidize Water to Dioxygen

Abstract

During the past four years we have witnessed a revolution in the field of water-oxidation catalysis, in which well-defined molecules are opening up entirely new possibilities for the design of more rugged and efficient catalysts. This revolution has been stimulated by two factors: the urgent need for clean and renewable fuel and the intrinsic human desire to mimic nature's reactions, in this case the oxygen-evolving complex (OEC) of the photosystem II (PSII). Herein we give a short general overview of the established basis for the oxidation of water to dioxygen as well as presenting the new developments in the field. Furthermore, we describe the new avenues these developments are opening up with regard to catalyst design and performance, together with the new questions they pose, especially from a mechanistic perspective. Finally the challenges the field is facing are also discussed.

Charge photo-accumulation and photocatalytic hydrogen evolution under visible light at an iridium(iii)-photosensitized polyoxotungstate

“…[1][2][3][4] In the past decades, molecular approaches have mostly focused on one hand on the design of photosensitive systems displaying long-lived photo-induced charge separation states to permit further electron transfers 5-10 and, on the other hand, on catalysts able to use these photogenerated charges for achieving either oxygen [11][12][13][14][15][16][17][18] or hydrogen evolution. [19][20][21][22][23][24] As these two reactions are multi-electronic processes while photosensitizers deliver electrons and holes sequentially, the charges need to be directed to a charge accumulation site.…”

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

“…The drawback lies in the intrinsic weakness of the biological components, requiring multiple repair strategies of both the inorganic core and the enzyme proteins. Similar stability issues due to oxidative damage during water oxidation affect most of the synthetic homogeneous molecular catalysts (5,6).…”

Visible Light Promoted Allylic C–H Oxidation

“…[8] This is because solar energy (visible light) is clean, easy to handle and an unlimited energy source having great prospects for the development of sustainable and eco-friendly protocols for organic synthesis. [9] Some pioneering researchers have dedicated to converting solar energy into chemical energy for chemical transformations [10,11] which includes a promising strategy for the application of photoredox catalysts to initiate single electron transfer processes have been developed. [12,13] The visible light photoredox catalysis has recently received much attention in organic synthesis owing to readily availability, sustainability, non-toxicity and ease of handling of visible light.…”