Mesoporous nitrogen-doped carbon nanoparticles with atomically dispersed iron sites (named mesoNC-Fe) are synthesized via high-temperature pyrolysis of an Fe containing ZIF-8 MOF. Hydrolysis of tetramethyl orthosilicate (TMOS) in the MOF framework prior to pyrolysis plays an essential role in maintaining a high surface area during the formation of the carbon structure, impeding the formation of iron (oxide) nanoparticles. To gain inside on the nature of the resulting atomically dispersed Fe moieties, HERFD-XANES, EXAFS and valence-to-core X-ray emission spectroscopies have been used. The experimental spectra (both XAS and XES) combined with theoretical calculations suggest that iron has a coordination sphere including a porphyrinic environment and OH/H₂O moieties responsible for the high activity in CO₂ electroreduction. DFT calculations demonstrate that CO formation is favored in these structures because the free energy barriers of *COOH formation are decreased and the adsorption of *H is impeded. The combination of such a unique coordination environment with a high surface area in the carbon structure of mesoNC-Fe makes more active sites accessible during catalysis and promotes CO₂ electroreduction.

The electrochemical reduction of CO₂ holds great promise for lowering the concentration of CO₂ in the Earth′s atmosphere. However, several challenges have hindered the commercialization of this technology, including energy efficiency, the solubility of CO₂ in the aqueous phase, and electrode stability. In this Minireview, we highlight and summarize the main advantages and limitations that metal–organic frameworks (MOFs) may offer in this field of research, either when used directly as electrocatalysts or when used as catalyst precursors.

We report the preparation and electrocatalytic performance of silver-containing gas diffusion electrodes (GDEs) derived from a silver coordination polymer (Ag-CP). Layer-by-layer growth of the Ag-CP onto porous supports was applied to control Ag loading. Subsequent electro-decomposition of the Ag-CP resulted in highly selective and efficient CO₂-to-CO GDEs in aqueous CO₂ electroreduction. Afterward, the metal-organic framework (MOF)-mediated approach was transferred to a gas-fed flow electrolyzer for high current density tests. The in situ formed GDE, with a low silver loading of 0.2 mg cm^-2, showed a peak performance of j_CO ≈ 385 mA cm^-2 at around -1.0 V vs RHE and stable operation with high FE_CO (>96%) at j_Total = 300 mA cm^-2 over a 4 h run. These results demonstrate that the MOF-mediated approach offers a facile route for manufacturing uniformly dispersed Ag catalysts for CO₂ electrochemical reduction by eliminating ill-defined deposition steps (drop-casting, etc.) while allowing control of the catalyst structure through self-assembly.

A nitrogen-doped carbon was synthesized through the pyrolysis of the well-known metal-organic framework ZIF-8, followed by a subsequent acid treatment, and has been applied as a catalyst in the electrochemical reduction of carbon dioxide. The resulting electrode shows Faradaic efficiencies to carbon monoxide as high as ∼78%, with hydrogen being the only byproduct. The pyrolysis temperature determines the amount and the accessibility of N species in the carbon electrode, in which pyridinic-N and quaternary-N species play key roles in the selective formation of carbon monoxide.