N-doped graphitic carbon encapsulating cobalt nanoparticles derived from novel metal–organic frameworks for electrocatalytic oxygen evolution reaction

Nitrogen-doped carbon catalysts with hierarchical porous structure are promising oxygen evolution reaction (OER) catalysts due to the faster mass transfer and better charge carrying ability. Herein, an exquisite high nitrogen-containing ligand was designed and readily synthesized from the low-cost biomolecule adenine. Accordingly, three new MOFs (TJU-103, TJU-104 and TJU-105) were prepared using the Co(II) or Mn(II) ions as metal nodes. Through rationally controlling pyrolysis condition, in virtue of the high nitrogen content in well-defined periodic structure of the pristine MOFs, TJU-104–900 among the derived MOFs with hierarchical porous structure, i.e., N-doped graphitic carbon encapsulating homogeneously distributed cobalt nanoparticles, could be conveniently obtained. Thanks to the synergistic effect of the hierarchical structure and well dispersed active components (i.e., C=O, Co‒N_x, graphitic C and N, pyridinic N), it could exhibit an overpotential of 280 mV@10 mA/cm² on carbon cloth for OER activity. This work provides the inspiration for fabrication of nitrogen-doped carbon/metal electrocatalysts from cost-effective and abundant biomolecules, which is promising for practical OER application.