The effect of confinement on the equilibrium reactive system containing nitrogen dioxide and dinitrogen tetroxide is studied by molecular simulation and the reactive Monte Carlo (RxMC) approach. The bulk-phase reaction was successfully reproduced and five all-silica zeolites (i.e. FAU, FER, MFI, MOR, and TON) with different topologies were selected to study their adoption behavior. Dinitrogen tetroxide showed a stronger affinity than nitrogen dioxide in all the zeolites due to size effects, but exclusive adsorption sites in MOR allowed the adsorption of nitrogen dioxide with no competition at these sites. From the study of the adsorption isotherms and isobars of the reacting mixture, confinement enhanced the formation of dimers over the full range of pressure and temperature, finding the largest deviations from bulk fractions at low temperature and high pressure. The channel size and shape of the zeolite have a noticeable influence on the dinitrogen tetroxide formation, being more important in MFI, closely followed by TON and MOR, and finally FER and FAU. Preferential adsorption sites in MOR lead to an unusually strong selective adsorption towards nitrogen dioxide, demonstrating that the topological structure has a crucial influence on the composition of the mixture and must be carefully considered in systems containing nitrogen dioxide.

We present a molecular simulation study on the most suitable zeolite topologies for hydrogen adsorption and storage. We combine saturation capacities, pore size distributions, preferential adsorption sites, and curves of heat of adsorption of hydrogen as a function of temperature (we call them heats of adsorption (HoA)-curve) to identify the optimal zeolites for storage and release of hydrogen. Then, we analyze the relation between the shape of the HoA-curve and the topology of the materials. We also evaluate the influence of incorporating Feynman-Hibbs effect on the adsorption behavior. We can establish different shapes on the HoA-curve depending on the uniformity or not of the pores of the zeolites. Parabola-like curves are observed in structures with one or similarly sized pores, whereas deviations from the parabola are found at low temperature for structures combining large and small pores. The Feynman-Hibbs quantum correction reduces the adsorption capacity of the materials affecting not only the saturation capacity but also the shape of the isotherms. From our results, the zeolites studied in this work can be considered potential candidates for the storage and release of hydrogen.