Efficient purification of xylene isomers, particularly the separation of para- / meta -xylenes (PX/MX), is industrially crucial but challenging. Here, we report a classical aluminum-based metal–organic framework (MIL-160) that exhibits an exceptional meta-selectivity in liquid-phase competitive adsorption of xylene isomers. The outstanding separation performance of MIL-160 for xylene isomers is confirmed by dynamic breakthrough experiments. The PX eluted first and breakthrough of MX didn’t occur until a long retention times, which is in accordance with the results observed from static adsorption experiment. Molecular simulations and calculations suggested that the largest affinity of MIL-160 toward MX, potentially due to the good fitness between the 1D square-shaped channel and MX. To improve the productivity of purified PX in continuous separation mode, we speculated that combining the MX-selective property of MIL-160 and the previously reported ortho -xylene (OX)-selective property of CAU-23 can enhance the separation effect between PX and the other two isomers. So, MIL-160 and CAU-23 were filled simultaneously in column and the effect of mass ratio of them on PX productivity was investigated. The results indicated that when the mass ratio of MIL-160 versus CAU-23 was 4:6, MX and OX almost simultaneously eluted and reached saturation, which can maximize the productivity of PX. This study offers a feasible strategy for isolating PX from xylene isomer with low energy consumption and high efficiency.
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.
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