Unless explicitly stated in the legend, properties were averaged over an (N, V, T ) trajectory of 1 ns for ReaxFF systems and 60 ps for ab initio. For ReaxFF simulations, frames are taken every 125 fs for the radial distribution function (RDF), bond angle distribution and coordination number, every 250 fs for the mean square displacement (MSD), every 10 ps for ring statistics and every 25 ps for pore statistics. For ab initio, those intervals are respectively of 0.5 fs, 5 fs, 0.5 ps and 0.5 ps.