Enlarging the porosity of metal-organic framework-derived carbons for supercapacitor applications by a template-free ethylene glycol etching method

In this work, hierarchically porous bimetallic zeolitic imidazolate framework (ZIF) particles (etched Zn₃₃Co₆₇-ZIF) exhibiting both micropores and mesopores have been designed and prepared through an ethylene glycol-assisted aqueous etching method. The etching process effectively increases the pore size, surface area, and pore volume of the bimetallic ZIF particles. After the thermal treatment, the etched Zn₃₃Co₆₇-ZIF particles are transformed into cobalt and nitrogen co-doped hierarchically porous carbon (i.e., etched Zn₃₃Co₆₇-C). Etched Zn₃₃Co₆₇-C has an increased mesoporosity, leading to an approximately 45% increase in its specific capacitance compared to the unetched one. In addition, etched Zn₃₃Co₆₇-C displays a higher capacitance retention (67%) than unetched Zn₃₃Co₆₇-C (41%) over a range of scan rates from 1 to 100 mV s⁻¹. The presented ethylene glycol-assisted aqueous etching process provides a facile template-free strategy to enlarge the porosity of MOFs and their corresponding porous carbons for improving their energy storage performance.