Single-step purification of para-xylene from xylene isomers through a synergistic combination of two robust aluminum-based metal–organic frameworks

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.