Rational Design of Vanadium-Decorated Aza-Triphenylene Covalent Organic Frameworks for Superior Hydrogen Storage: A Computational Study

This study investigates the potential of newly synthesized Aza-triphenylene-based covalent organic frameworks (Aza-COF) decorated with vanadium metal for efficient hydrogen storage applications. Decorating each unit cell of the Aza-triphenylene COF with six vanadium(V) atoms achieves a high hydrogen storage capacity of up to 6.67 wt %, with each V atom adsorbing up to seven H2 molecules. The average H2 binding energy of −0.46 eV ensures an optimal balance between adsorption and desorption, meeting the U.S. Department of Energy (DOE) guidelines for practical hydrogen storage. The strong V-decorated Aza-COF interaction arises from charge transfer from V to the 2D framework, while electric field-induced polarization enhances van der Waals interactions, boosting adsorption energy. High kinetic stability is demonstrated by a substantial barrier energy of 6.06 eV, preventing vanadium migration and clustering, while ab initio molecular dynamics at 300 K and phonon spectrum analysis confirm thermodynamic and dynamic stability, respectively. The system also exhibits suitable desorption kinetics with desorption temperatures of 425 K at 5 bar and 453 K at 12 bar, indicating its suitability for practical applications. Combining high gravimetric capacity with moderate binding energies, this study provides a theoretical foundation for experimental exploration of V-decorated Aza-COF as advanced hydrogen storage materials.