Contemporary Strategies for Immobilizing Metallophthalocyanines for Electrochemical Transformations of Carbon Dioxide

Abstract

Metallophthalocyanine (PcM) coordination complexes are well-known mediators of the electrochemical reduction of carbon dioxide (CO2). They have many properties that show promise for practical applications in the energy sector. Such properties include synthetic flexibility, a high stability, and good efficiencies for the reduction of CO2 to useful feedstocks, such as carbon monoxide (CO). One of the ongoing challenges that needs to be met is the incorporation of PcM into the heterogeneous materials that are used in a great many CO2-reduction devices. Much progress has been made in the last decade and there are now several promising approaches to incorporate PcM into a range of materials, from simple carbon-adsorbed preparations to extended polymer networks. These approaches all have important advantages and drawbacks. In addition, investigations have led to new proposals regarding CO2 reduction catalytic cycles and other operational features that are crucial to function. Here, we describe developments in the immobilization of PcM CO2 reduction catalysts in the last decade (2013 to 2023) and propose promising avenues and strategies for future research.

Dramatic Improvement of Homogeneous Carbon Dioxide and Bicarbonate Electroreduction Using a Tetracationic Water-Soluble Cobalt Phthalocyanine

“…We recently reviewed several of those systems. 80 Perhaps the most systematic study is for unsubstituted CoPc deposited on carbon paper, 12 where highly dispersed systems can achieve turnover frequency (TOF) values of about 10 2 s −1 . Similar TOF values were determined for a highly dispersed octaethoxy-CoPc system on carbon nanoparticles.…”

“…As pointed out in that work, there are many more examples of heterogeneous CO 2 reduction systems based on CoPc. We recently reviewed several of those systems . Perhaps the most systematic study is for unsubstituted CoPc deposited on carbon paper, where highly dispersed systems can achieve turnover frequency (TOF) values of about 10 2 s –1 .…”

Inducing ring distortions in unsubstituted metallophthalocyanines using axial N-heterocyclic carbenes

“…Phthalocyanines (PcH 2 ) have a diverse coordination chemistry and are used in applications ranging from colourants to electrocatalysts. 1–8 The simplest complexes are those of ring-unsubstituted PcH 2 , for which many metal-substituted PcM congeners that span the periodic table are known. However, the extended π system, and the resultant rigid, planar structure of unsubstituted PcM complexes result in a strong tendency for them to aggregate.…”