Pendant amine-promoted complete eight-electron photoreduction of CO2 to methane by a molecular nickel catalyst
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Updated: Jun 13, 2026

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction
Published on: April 10, 2018
Chandan Das1, Liton Seikh1, Abhishek Saini1
1Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India arnab.dutta@iitb.ac.in.
Abstract:
Solar-driven CO2 reduction offers a sustainable route to carbon neutrality by converting greenhouse gases into value-added fuels. Here, we report a secondary coordination sphere design strategy that directs CO2 photoreduction selectivity toward methane (CH4). A redox-active Ni complex (C1), incorporating two (6-amino-2-(phenylazo)pyridine) ligands with a pendant amine, exhibits markedly enhanced CH4 selectivity compared to control complexes lacking the pendant -NH2 group. Systematic evaluation of sacrificial donors, proton sources, and photosensitizers identified a dimeric Cu(i)-based photosensitizer (Cu-PS-1) as a cost-effective alternative to Ir-based systems, achieving TONCO2→CO = 4789, TONCO2→CH4 = 1130, and TONCO→CH4 = 3102, rivalling Ir-PS-1. Operando UV-vis, FTIR, and EPR spectroscopy, together with DFT calculations, revealed a stepwise 8e-/8H+ reduction pathway in which the pendant -NH2 group stabilizes key COOH and CH x intermediates through hydrogen bonding, lowering activation barriers and steering selectivity toward CH4. These results establish OCS engineering as a powerful design principle for earth-abundant molecular catalysts and highlight new opportunities for selective CO2-to-CH4 conversion in artificial photosynthesis and carbon valorization.
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