Efficient liquid-phase adsorptive separation between p- and m-Chlorotoluene by a metal-organic framework Mn-dhbq

The p -chlorotoluene (PCT) and m -chlorotoluene (MCT) are indispensable chemical intermediates in pharmaceuticals, agrochemicals, and material synthesis. However, the similar physical and chemical properties of the PCT and MCT make their efficient separation a severe challenge in the current chemical separation field. In this study, a metal-organic framework named Mn-dhbq (dhbq = 2,5-dihydroxy-1,4-benzoquinone) is employed to achieve highly efficient separation of PCT/MCT in a solvent system with 1,3,5-trimethylbenzene. The Mn-dhbq exhibits the adsorption capacity of 208 mg/g for PCT and 72 mg/g for MCT at 25 °C, with initial concentration of 20 % for both PCT and MCT. Notably, the dual-site Langmuir-Freundlich selectivity is 38 with the concentration of 1 % for PCT and MCT. Density functional theory (DFT) calculations reveal differences in the amount of charge transfer and interaction sites between the framework and adsorbate, and these factors collectively contribute to the selective separation of PCT and MCT by Mn-dhbq.