Computer-aided prediction of structure and hydrogen storage properties of tetrakis(4-aminophenyl)silsesquioxane based covalent-organic frameworks

Abstract

With the aid of computer simulation, we have designed four covalent-organic frameworks based on tetrakis(4-aminophenyl)silsesquioxane (taps-COFs) and their hydrogen storage properties were predicted with grand canonical Monte Carlo (GCMC) simulation. The structural parameters and physical properties were investigated after the geometrical optimization. The accessible surface for H2 molecule (5564.68–6754.78 m2/g) were estimated using the numerical Monte Carlo integration and the pore volume (4.06–10.74 cm3/g) was evaluated by the amounts of the containable nonadsorbing helium molecules at low pressures and room temperature. GCMC simulation reveals that at 77 K, tapsCOF1 has the highest gravimetric H2 adsorption capacity of 51.43 wt% and tapsCOF3 possesses the highest volumetric H2 adsorption capacity of 58.51 g/L. Excitedly, at room temperature of 298 K, the gravimetric hydrogen adsorption capacities of tapsCOF1 (8.58 wt%) and tapsCOF2 (8.20 wt%) have exceeded the target (5.5 wt%) of onboard hydrogen storage system for 2025 set by the U.S Department of Energy.