2.2.1. Nitrogen Physisorption

Nitrogen physisorption measurements were performed at −196 ◦C using a Micromeritics Tristar II Plus sorptometer (MICROMERITICS, Norcross, GA, USA). The sample (~400 mg) was outgassed at 200 ◦C for 2 h in vacuum prior to the sorption experiment. The surface area was calculated using the BET equation [25], and the total pore volume, Vtot, was measured as the adsorbed amount of N<sup>2</sup> at P/P<sup>0</sup> values near 0.98. Pore size distribution was determined by the BJH method [26] applied to the N<sup>2</sup> adsorption isotherm branch [27,28].
