Exposed surface-area-to-volume ratio dependence of water vapor dynamics on fixed powder bed samples at 70% RH and 22 °C. (a) Water vapor adsorption of studied MOFs with a packing porosity of ~0.65–7 and a sample depth of 2 mm. Ti-MIL-125 (black), Ti-MIL-125-NH2 (orange), Cr-MIL-101 (blue), Zr-MOF-808 (green), and Zr-UiO-66-NH2 (yellow). (b) Water vapor adsorption of Cr-MIL-101 at a packing porosity of ~0.65–7 and sample depth of 1 (blue), 2(green), 5 (yellow), and 10 (red) mm. Experimental results are shown as solid spheres, LDF fitted plot as a dashed line, and pseudo-zero order fitted as a solid line in representative color.