Highly Efficient Electroconversion of CO2 into CH4 by a Metal-Organic Framework with Trigonal Pyramidal Cu(I)N3 Active Sites

High-efficiency electrocatalysts for CO2 reduction reaction are extremely desirable to produce valuable hydrocarbon productions, as well as addressing the current environmental challenges. In this work, we introduce a Cu-based metal-organic framework as a catalyst for the efficient and selective reduction of CO2 to CH4 in neutral aqueous electrolytes. Detailed examination of [Cu4ZnCl4(btdd)(3)] (Cu-4-MFU-4l, H(2)btdd = bis(1H-1,2,3-triazolo-[4,5-b],[4',5'-i])dibenzo-[1,4]-dioxin) revealed the highest activity for yielding methane with a Faradaic efficiency of 92%/88% and a partial current density of 9.8/18.3 mA cm(-2) at a potential of -1.2/1.3 V (vs RHE). In situ X-ray absorption and infrared spectroscopy spectra, as well as density functional theory calculations, revealed that the in situ generated trigonal pyramidal Cu(I)N-3 acts as the electrochemical active site and that the strong coordination ability of the Cu(I)N-3 site and the synergistic effect of adjacent aromatic hydrogen atoms, via hydrogen-bonding interactions, play an important role in stabilizing the key intermediates of carbon dioxide reduction and inhibiting the hydrogen evolution reaction, thus showing a high performance of electroreduction of CO2 to CH4.

Automated summary

In this study, a Cu-based metal-organic framework was introduced as a catalyst for the efficient and selective reduction of CO2 to CH4. The in situ-generated trigonal pyramidal Cu(I)N-3 was identified as the electrochemical active site, while the hydrogen-bonding interactions of adjacent aromatic hydrogen atoms played a key role in stabilizing key intermediates of carbon dioxide reduction and inhibiting the hydrogen evolution reaction, demonstrating a high performance in electroreduction of CO2 to CH4.