Unraveling the efficient separation of positional phenylethanol isomers by aluminum-based metal–organic frameworks: The role of pore geometry and multiple molecular interactions

Adsorption-based separation of 2-phenylethanol (2-PE) and 1-phenylethanol (1-PE) is crucial yet challenging in the petrochemical industry. In this study, we report that an ultra-micropore aluminum-based metal–organic framework (Al-MOF) (i.e., CAU-23) exhibits higher 2-PE/1-PE selectivity (6.12) and 2-PE adsorption capacity (2.52 mmol g −1 ) in liquid phase compared to its pseudo-isostructural analogue of Al-MOFs, MIL-160 and MOF-303 at 293 K. The micropore diffusion model was employed to give the best fit to the adsorption kinetics of the CAU-23 with a rate achieved higher than MIL-160 and MOF-303. Computational analysis confirmed that 2-PE preferential adsorption stems from CAU-23′s well-matched pore geometry which enables efficient molecular confinement. In combination of inspecting the static adsorption properties of 2-PE and 1-PE onto CAU-23, we found that the superior affinity of CAU-23 toward 2-PE over 1-PE originates from entropy and enthalpy effect. The remarkable 2-PE/1-PE separation capability of CAU-23 was confirmed through breakthrough curve analysis (separation factor ≈ 4). As the first Al-MOF developed for 2-PE/1-PE separation, CAU-23 offers valuable insights into the design of advanced 2-PE-selective adsorbents.