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

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. Here, 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.