• MIL-53(Al) is known for swelling upon adsorption, thus opening its pores. The crystal structure we matched in this study is a closed-pore model with 0.28 cm 3 g -1 of geometrical pore volume (refcode: SABWAU01). Using an open-pore model instead, e.g., DOYBEA, we obtain a geometric pore volume of 0.55 cm 3 g -1 , about twice its closed-pore configuration. Most of the measured pore volumes fall inside the range between the open and closed-pore model.