Zeolitic Imidazolate Frameworks (ZIF) find application
in storage
and dissipation of mechanical energy. Their distinctive properties
linked to their (sub)nanometer size and hydrophobicity allow for water
intrusion only under high hydrostatic pressure. Here we focus on the
popular ZIF-8 material investigating the intrusion mechanism in its
nanoscale cages, which is the key to its rational exploitation in
target applications. In this work, we used a joint experimental/theoretical
approach combining in operando synchrotron experiments during high-pressure
intrusion experiments, molecular dynamics simulations, and stochastic
models to reveal that water intrusion into ZIF-8 occurs by a cascade
filling of connected cages rather than a condensation process as previously
assumed. The reported results allowed us to establish structure/function
relations in this prototypical microporous material, representing
an important step to devise design rules to synthesize porous media.