Proton-Assisted Reduction of CO₂ by Cobalt Aminopyridine Macrocycles

Abstract

We report here the efficient reduction of CO2 to CO by cobalt aminopyridine macrocycles. The effect of the pendant amines on catalysis was investigated. Several cobalt complexes based on the azacalix[4](2,6)pyridine framework with different substitutions on the pendant amine groups have been synthesized (R = H (1), Me (2), and allyl (3)), and their electrocatalytic properties were explored. Under an atmosphere of CO2 and in the presence of weak Brønsted acids, large catalytic currents are observed for 1, corresponding to the reduction of CO2 to CO with excellent Faradaic efficiency (98 ± 2%). In comparison, complexes 2 and 3 generate CO with TONs at least 300 times lower than 1, suggesting that the presence of the pendant NH moiety of the secondary amine is crucial for catalysis. Moreover, the presence of NH groups leads to a positive shift in the reduction potential of the Co(I/0) couple, therefore decreasing the overpotential for CO2 reduction.

Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

“…[1][2][3] Extensive utiliza tion of fossil fuels has caused enormous CO 2 emission as the culprit for global environmental changes. [6,7] In the previous decades, traditionally biological and electrocata lytic techniques have been widely inves tigated. [6,7] In the previous decades, traditionally biological and electrocata lytic techniques have been widely inves tigated.…”

Highly Efficient Photocatalytic System Constructed from CoP/Carbon Nanotubes or Graphene for Visible‐Light‐Driven CO2 Reduction

“…The C=O bond lengths of 1.211 and 1.280 Å in the V‐configuration are considerably longer than those of 1.172 and 1.169 Å in the linear molecule (Figure S8). The calculation results indicate that high catalytic activity arises from P defects on the CoP surface . When the H atom of a proton donor far from the P atom of the CoP surface (6.682 Å) approaches a P⋅⋅⋅H distance of 1.410 Å, the interaction between the H atom and the O atom of CO 2 is accompanied by a H⋅⋅⋅O distance of 3.705 Å, and energy of 3.73 eV is released.…”

Recent Trends, Benchmarking, and Challenges of Electrochemical Reduction of CO2 by Molecular Catalysts

“…[77] As previously reported, [75] solution-phase hybridization of cobalt phthalocyanine and MWCNT (in addition to carbon black and graphene) was adopted to modify the electrodes. [78] In 2017, inspired from the catalyst design of the aforementioned Co-aminopyridine macrocycle, [78] Roy et al [67] extended the structures to form a novel family of Co complexes with pendant amines present in diphosphine ligands, P R 2 N R' 2. CPE on a CO 2 saturated aqueous media yielded a TON CO of 97 000 with FE CO of ≈90% at E appl = −0.63 V versus RHE for 10 h. Substitution in the molecular structure with electron-withdrawing cyano groups resulted in a high FE CO of 98% at E appl = −0.63 V versus RHE and negligible current decay over an hour, demonstrating the possibility of catalyst tuning through modification of electronic properties.…”