Guest-Specific Double- or Single-Step Adsorption in a Flexible Porous Framework Based on a Mixed-Ligand System

A 2D flexible metal−organic porous solid, {[Ni(1,3-adc)(bpp)(H2O)2](H2O)(EtOH)}n (1), has been synthesized using flexible organic linkers. The desolvated framework, {[Ni(1,3-adc)(bpp)]}n (1′), undergoes structural contraction and exhibits double-step hysteretic adsorption for CO2, H2O, and MeOH and single-step gate-opening behavior with EtOH. These observations are correlated with the effect of the polarity and window dimension of the pore to the corresponding adsorbate molecules.