The expected usage of pristine B4CN3 nanosheets for practical hydrogen storage purpose is analyzed using periodic DFT computations. The results of this study indicated that the desired nanosheet of B4CN3 will form a promising material that can take up to 6H2 molecules with a massive hydrogen storage capacity of 11.0 wt% and adsorption energies between 0.227 and 0.616 eV. Hydrogen desorption from the B4CN3(6H2) framework happens at TD = 291 K and the pressure of one atmosphere, which is under environmental conditions. This is a momentous result, which indicates the potential application of the B4CN3 adsorptive material for practical hydrogen storage purposes.