For instance, it was shown that intrusion of highly concentrated LiCl solution (∼ 20 M) in silicalite-1 increases intrusion pressure from 96 MPa to 280 MPa, resulting in an increase of stored energy from 10 J/g to 31 J/g. Since this pioneering work, the nature and concentration of electrolyte on the intrusion and extrusion pressure and energetic properties of zeosils has been widely investigated. In addition to zeosils, that are the scope of this work, we note that intrusion and extrusion of pure water and electrolyte solutions have also been investigated in other microporous materials, such as metal-organic frameworks ZIF-8, ZIF-71 and other ZIF materials, as well as MAF-6. Although the mechanism of water intrusion in hydrophobic microporous materials has been highlighted by Grand Canonical Monte Carlo (GCMC) simulations, the mechanism of electrolyte intrusion is still under debate: it is characterized by an increase of intrusion pressure that depends both on electrolyte nature and concentration. Several hypotheses have been proposed such as ion desolvation, osmotic effect, 41 confinement effect or increase of solid-liquid interfacial tension. Recently, it has been shown that intrusion of NaCl electrolyte solution in chabazite and LTA-type zeosils occurs in two steps. First, only water molecules penetrate into the nanocages at respectively 44 and 36 MPa in chabazite and LTA-type zeosils. Then, ions penetrate at a much higher pressure of respectively 260 MPa and 140-240 MPa. This is supported by previous MC simulations performed by Zamfir and co-workers where NaCl electrolyte penetrates a two-dimensional planar hydrophobic nanopores once water has been intruded inside it. The initial step consisting of intrusion of only water molecules is crucial for energy storage applications. Thus, the dependence of the intrusion pressure with the nature and concentration of electrolyte requires further investigation, which is the object of this work by relying on our recent implementation of molecular simulations with an osmostat for electrolyte aqueous solution. Briefly, the osmostat is based on a hybrid Monte Carlo move using nonequilibrium molecular dynamics, named Nonequilibrium Candidate Monte Carlo (NCMC), proposed by Nilmeier 56 and later applied by Ross and co-workers to sample the distribution of NaCl electrolyte around biomolecules. We previously calculated the chemical potential of ion exchange ∆µ CnAm (P ) in the semi-grand canonical ensemble for "alchemically" transforming (n+m) water molecules chosen randomly into an electrolyte unit C n A m (where C m+ and A n-denote respectively the cation and the anion electrolyte) in bulk electrolyte solution at fixed concentration. We used a modified version of the Widom insertion method except that the work performed during the alchemical transformation W (n+m)H 2 O→CnAm (refered as the "alchemical work" to be noted W CnAm ) is taken into account, instead of the difference of energy between the initial and final step of the alchemical transformation. This chemical potential used in combination with NCMC moves to insert or delete ions at constant number of particles in the system defines the osmotic ensemble, where the fictitious reservoir is an electrolyte solution at a concentration imposed by the chemical potential.