2D MOFs Containing Bis(azabenzimidazole) and Dicarboxylate Moieties for the Efficient Oxygen Evolution Reaction and CO2Sorption

With the rapid advancement of electronic technology, the necessity for efficient electrode materials has been tremendously increasing. With this endeavor, the design of cost-saving, environment-friendly, and stable electrocatalysts from earth-abundant transition elements for water splitting is immensely desired. To this contribution, herein, we have aimed to design two stable Co(II)- and Ni(II)-containing redox-active metal–organic frameworks (Co-MOF and Ni-MOF) with a nitrogen-rich linear bis(azabenzimidazole) ligand and electron-rich dicarboxylic acids and explored the redox-active metal–organic frameworks (MOFs) as efficient heterogeneous catalysts for oxygen evolution reaction (OER) and CO2 sorption studies. The structural analysis of Co-MOF shows that it exhibits a double-walled square grid-type two-dimensional structure, whereas Ni-MOF exhibits a rectangular grid-type two-dimensional layered structure. Further, three-dimensional packing of both MOFs is formed by two-dimensional (2D) metal–ligand coordination layers via N–H···O hydrogen bonding interactions with the imidazole moiety and solvent molecules, resulting in one-dimensional cavities. These cavities have void spaces of 27.6 and 33.2% for Co-MOF and Ni-MOF, respectively, which are occupied by water molecules in Co-MOF and dimethylformamide (DMF) molecules in Ni-MOF. Electrochemical studies of these pristine MOFs infer that both MOFs display efficient OER activity in alkaline solutions. These MOFs demand overpotentials of 470 and 450 mV to generate a current density of 10 mA/cm2, which is nearly equivalent to 10% solar energy conversion efficiency. The 2D layers with nitrogen-rich ligands and oxygen-rich linkers are expected to promote better diffusion of electrons and protons in the course of the electrocatalytic process. The presence of hydrophilic channels further promoted to adsorb considerable amounts of CO2 gas (46 and 15 cm3/g, respectively) at 273 K and 1 bar pressure.