Restructuring Metal–Organic Frameworks to Nanoscale Bismuth Electrocatalysts for Highly Active and Selective CO2 Reduction to Formate

Recently, a large number of nanostructured metal‐containing materials have been developed for the electrochemical CO2 reduction reaction (eCO2RR). However, it remains a challenge to achieve high activity and selectivity with respect to the metal load due to the limited concentration of surface metal atoms. Here, it is reported that the bismuth‐based metal–organic framework Bi(1,3,5‐tris(4‐carboxyphenyl)benzene), herein denoted Bi(btb), works as a precatalyst and undergoes a structural rearrangement at reducing potentials to form highly active and selective catalytic Bi‐based nanoparticles dispersed in a porous organic matrix. The structural change is investigated by electron microscopy, X‐ray diffraction, total scattering, and spectroscopic techniques. Due to the periodic arrangement of Bi cations in highly porous Bi(btb), the in situ formed Bi nanoparticles are well‐dispersed and hence highly exposed for surface catalytic reactions. As a result, high selectivity over a broad potential range in the eCO2RR toward formate production with a Faradaic efficiency up to 95(3)% is achieved. Moreover, a large current density with respect to the Bi load, i.e., a mass activity, up to 261(13) A g−1 is achieved, thereby outperforming most other nanostructured Bi materials. A bismuth‐containing metal–organic framework transforms to an ensemble of bismuth nanoparticles dispersed in a porous organic matrix under electrochemical conditions in aqueous solution. When used as a catalyst in the electroreduction of carbon dioxide, it selectively produces formate (≈95%) with large activity relative to the metal content (≈261 A g−1), outperforming previously reported bismuth‐based materials.