Molecularly Engineered Silver(I) Gel Catalysts for Industrial-Level CO₂ Electroreduction

Power-to-X strategies are a key approach for coupling renewable energy generation with storage and utilization pathways. Because renewable sources such as solar and wind are intermittent, surplus electricity must be converted into chemical energy carriers, including hydrogen, fuels, and chemical feedstocks. In this context, the capture and electrochemical conversion of CO₂ into valuable products is particularly attractive, as it supports a circular carbon economy and mitigates greenhouse gas emissions. Herein, we report the solvochemical and mechanochemical synthesis and implementation of a triazine-based ligand system, 2,4,6-tri-(1H-pyrazol-1-yl)-1,3,5-triazine (TPT-1), and its silver(I) complexes for electrochemical CO₂ reduction. TPT-1 was synthesized via heteroaryl nucleophilic substitution of chlorine on a 1,3,5-triazine ring by pyrazolate. Subsequent metalation yielded the silver complexes Ag(TPT-1)₂ and polymeric Ag₂(TPT-1)₂, which were characterized by nuclear magnetic resonance (NMR), ultraviolet/visible (UV/vis), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and high-resolution mass spectrometry (HRMS). Electrocatalytic activity was first investigated by homogeneous cyclic voltammetry in CH₃CN and subsequently under heterogeneous conditions in H-type and custom-built zero-gap electrochemical cells. The silver(I) complexes exhibited stable and selective CO₂-to-CO conversion, achieving Faradaic efficiencies of ∼80%, energy efficiencies of 24%, and single-pass conversions of 20% at a constant current density of 200 mA cm^-2.