Nanocrystal/Metal-Organic Framework Hybrids as Electrocatalytic Platforms for CO₂ Conversion

The tunable chemistry linked to the organic/inorganic components in colloidal nanocrystals (NCs) and metal-organic frameworks (MOFs) offers a rich playground to advance the fundamental understanding of materials design for various applications. Herein, we combine these two classes of materials by synthesizing NC/MOF hybrids comprising Ag NCs that are in intimate contact with Al-PMOF ([Al₂ (OH)₂ (TCPP)]) (tetrakis(4-carboxyphenyl)porphyrin (TCPP)), to form Ag@Al-PMOF. In our hybrids, the NCs are embedded in the MOF while still preserving electrical contact with a conductive substrate. This key feature allows the investigation of the Ag@Al-PMOFs as electrocatalysts for the CO₂ reduction reaction (CO₂ RR). We show that the pristine interface between the NCs and the MOFs accounts for electronic changes in the Ag, which suppress the hydrogen evolution reaction (HER) and promote the CO₂ RR. We also demonstrate a minor contribution of mass-transfer effects imposed by the porous MOF layer under the chosen testing conditions. Furthermore, we find an increased morphological stability of the Ag NCs when combined with the Al-PMOF. The synthesis method is general and applicable to other metal NCs, thus revealing a new way to think about rationally tailored electrocatalytic materials to steer selectivity and improve stability.