Porphyrin-based graphene oxide frameworks with ultra-large d-spacings for the electrocatalyzation of oxygen reduction reaction

Graphene oxide frameworks (GOFs) have attracted a great deal of attention because of their unique functional building blocks, and tunable structures and properties. Herein, a series of porphyrin-based GOFs with crystalline lamellar structures were synthesized via esterification between boronic acid groups of porphyrins and hydroxyl groups of GO sheets. These GOFs have ultra-large d-spacings of up to 26.0 angstrom, and they were reduced by facile electrochemical reduction. The resulting reduced GOFs (rGOFs) can be used as catalysts for oxygen reduction reaction (ORR). Electrochemical reduction improved the conductivities of GOFs, accelerating the charge transfer of ORR. The rGOF with Co-porphyrin showed the most positive onset potential of ORR at 0.89 V (vs. RHE, reversible hydrogen electrode), while the rGOF with Fe-porphyrin exhibited the highest catalytic efficiency through an approximately four-electron process. This study provides a new insight for the development of GOFs using multi-functional macrocyclic molecules, revealing their promising applications in electrocatalysts.