Metal-Phthalocyanine-Based Two-Dimensional Conjugated Metal-Organic Frameworks for Electrochemical Glycerol Oxidation Reaction

Abstract

Electrochemical glycerol oxidation reaction (GOR) is a promising candidate to couple with cathodic reaction, like hydrogen evolution reaction, to produce high-value product with less energy consumption. Two dimensional conjugated metal–organic frameworks (2D c-MOFs), comprising square-planar metal-coordination motifs (e.g., MO₄, M(NH)₄, MS₄), are notable for their programable active sites, intrinsic charge transport, and excellent stability, making them promising catalyst candidates for GOR. In this study, we introduce a novel class of 2D c-MOFs electrocatalysts, M₂[NiPcS₈] (M=Co/Ni/Cu), which are synthesized via coordination of octathiolphthalocyaninato nickel (NiPc(SH)₈) with various metal centers. Due to a fast kinetic and high activity of CoS₄ sites for GOR, the electrocatalytic tests demonstrate that Co₂[NiPcS₈] supported on carbon paper displays a low GOR potential of 1.35 V vs. RHE at 10 mA cm⁻², significantly reducing the overall water-electrolysis-voltage reduction by 0.27 V from oxygen evolution reaction to GOR, thereby outperforming Ni₂[NiPcS₈] and Cu₂[NiPcS₈]. Additionally, we have determined that the GOR activity of CoX₄ linkage sites varies with different heteroatoms, following an experimentally and theoretically confirmed activity order of CoS₄>CoO₄>Co(NH)₄. The GOR performance of Co₂[NiPcS₈] not only demonstrate superior performance among non-noble metal complex, but also provides critical insights on designing high-performance MOF electrocatalysts upon optimizing the electronic environment of active sites.