Molecular catalysis of CO₂ reduction: recent advances and perspectives in electrochemical and light-driven processes with selected Fe, Ni and Co aza macrocyclic and polypyridine complexes

Abstract

Recent developments in (photo)electrochemical CO2 reduction combining Fe, Ni, and Co molecular complexes and (semi)conductive materials have led to high catalytic performances.

Replacing Pyridine with Pyrazine in Molecular Cobalt Catalysts: Effects on Electrochemical Properties and Aqueous H2 Generation

“…Catalysts that can transform typically inert but sustainable reagents, such as light and water, to generate high-value fuels are absolutely critical to mitigating atmospheric CO 2 accumulation and climate disruption [1][2][3][4][5]. The development of such catalytic systems can be accelerated using molecular complexes, which provide the opportunity to investigate the impact of chemical and electronic structures on catalytic mechanisms and activities with atomic-level resolution [6][7][8][9][10]. Furthermore, molecular catalysts provide the critical ability to investigate in detail the role of both the active center and supporting environment, as well as their interaction.…”

Enabling storage and utilization of low-carbon electricity: power to formic acid

“…Electrochemical CO2 reduction reactions (eCO2RR) using renewable energy offers a direct pathway for power-to-formic acid where CO2 is utilized as a storage medium as well as a feedstock for valuable fuels/chemicals and has previously been discussed in various perspectives, review articles and book chapters. [162][163][164][165][166][167][168][169][170][171] Electrocatalysis has several advantages: 1) the process can be controlled by adjusting the potentials and reaction temperatures, 2) the electrolytes can be recycled in many cases, 3) the set-up is modular, compact, and easy to scale up, 4) the reaction may be conducted at room temperature and atmospheric pressure, and 5) direct use of renewable and/or low-carbon electricity is applicable. eCO2RR is, in general, considered to involve three main steps: 1) CO2 activation by chemical adsorption of CO2 on the surface of a catalyst, 2) electron (e -) and proton (H + ) transfer to break C-O bonds and/or form C-H bonds, and 3) rearrangement of product(s) followed by desorption from the electrode surface and diffusion into electrolyte.…”

“…Highly active transition metal complexes are the promising candidates to overcome challenges associated with metal, oxides, and bio(inspired)-catalysts. 166,170,180,281,282 Because of the well-defined structures of the molecular complexes, fine-tuning of the chelating abilities as well as the steric, electronic and electrostatic effects of the ligand framework is conceivable, thus opening opportunities towards further mechanistic and spectroscopic studies. In analogy to the CO2 hydrogenation catalysts, in some cases, metal hydride intermediates may play an essential role during CO2 insertion to produce formate/FA selectively.…”

“…288 Development of molecular catalysts based on 1 st row earth-abundant transition metals for CO2 electroreduction has been a thriving area since the discovery of [Ni(cyclam)] +2 (cyclam: 1,4,8,11-tetraazacyclotetradecane) (147) catalyzed eCO2RR-toformate in DMF in the late 80s by Collin et al 289 These studies have revived enormously in recent years and stimulated new results. 170 The Berben group has investigated metalmetal clusters with delocalized bonding within the metal core and electron delocalization extending out to electron withdrawing CO ligands for eCO2RR. 290 A Fe-carbonyl cluster containing an interstitial nitride, [Fe4N(CO)11L] - (148), was found to show poor selectivity towards formate in the presence of a weak acid in MeCN, but good formate selectively over H2 in pH of 5−13 in aqueous buffer and in MeCN/H2O (95/5 v/v) ( Fig.…”

Substituent-induced electronic localization of nickel phthalocyanine with enhanced electrocatalytic CO2 reduction

“…27,28 The electron-donating substituents tend to denote more electrons into the π conjugation system of phthalocyanine ligand, which is bene cial to the electronic localization. 29,30 The amino and hydroxyl with lone pair electrons from the 2p orbit of N or O exhibit the prominent electron-donating property via p-π conjugation. 31,32 Compared with the hydroxyl, amino with a low electronegativity of N leads to interior inductive effect and thus shows preferable electron-donating ability.…”