As predicted by optimistic theoretical calculations, hexagonal boron nitride nanosheets with thin layers and elemental doping are considered promising media for hydrogen storage. To explore its hydrogen storage performance experimentally, a hexagonal boron nitride nanosheets consisting of only 6 atomic layers with 7 at. % O and 3 at. % F functionalization is prepared through a creative two-step synthesis. Moreover, the hydrogen adsorption at 77 and 298 K under different pressures is systematically measured. When operated in 6 MPa conditions, the hydrogen capacity of h-BNNS at 77 K can reach 1.43 wt %, which is almost three times higher than that at 298 K. By combining experimental data with first-principles calculations, the interaction mechanism between h-BNNSs and H