Hydrogen storage in ordered and disordered phenylene-bridged mesoporous organosilicas

Abstract

Novel hexagonal Periodic Mesoporous Organosilicas (PMOs) and Disordered Mesoporous Organosilicas (DMOs) were synthesized by hydrolysis of 1,4-bis(trialkoxylsilyl) benzene precursor in alkaline aqueous solutions of different alkyl-trimethyl ammonium cations and evaluated for their hydrogen storage capacity. The PMO materials exhibit regular hexagonal pore arrangement and specific surface area between 640 and 782 m2 g−1 whereas the DMO materials have specific surface area that lies between 650 and 910 m2 g−1. The storage capacity of the materials is discussed in terms of number of molecules per surface unit. The materials exhibit a reversible hydrogen excess surface adsorption capacity up to 2.10 wt% at 6 MPa and 77 K. DFT calculations were performed to define the binding strength of hydrogen with the pore walls indicated an interaction energy value of −0.55 Kcal mol−1, higher than the interaction energy value of hydrogen with a single benzene or a benzene incorporated in the IRMOR-1 walls. Grand Canonical Monte Carlo (GCMC) simulations showed that no hydrogen molecule can be inserted inside the wall structure of the materials.