The complex configuration, H₂ adsorption binding energy, magnetic, and optical properties of FAU zeolites with Ag cations loaded by ion exchange in the vacant dielectric cavities were investigated by employing the first-principles calculations with all-electron-relativistic numerical atom-orbitals scheme and the Metropolis Monte Carlo molecular simulations. The visible absorption spectrum peaked at distinct wavelengths arranging from red or green to blue colors when changing the net charge load, due to the produced various redox states of Ag cations exchanging at multiple Li⁺-substituted sites. The spin population analyses indicate the ferrimagnetic coupling between Al⁻O⁻Si framework and Ag cations originates from the major ferromagnetic spin polarization in Ag cation cluster coordinating with sodalite cages, with the net spins appreciably depending on the Ag content and exchange site. The H₂ adsorption capacities and binding energies represent significant dependence on the content, location, and electronic property of Ag cations introduced into the FAU zeolites. The evident decrease of H₂ adsorption binding energy with increased loading concentration demonstrates repulsive interaction between H₂ molecules and heterogeneous adsorption configuration on Ag cations. The adsorption sites of H₂ sorted by the binding energy with different adsorption configurations were correlated with exchange sites of Ag cations under different Ag loading to comprehend the H₂ adsorption mechanism.
Keywords: FAU zeolite; first-principles calculation; hydrogen storage; molecular simulation; silver cluster.