Selective Adsorption of <i>p</i>-Xylene from Xylene Isomers with Self-Adaptive Hydrogen-Bonded Organic Frameworks

The xylenes play an important role in modern industry and are mainly produced in the petrochemical industry. However, the selective adsorption and separation of xylene isomers are challenging due to their similar molecular sizes and boiling points. In this study, a flexible molecule, CHTA, was utilized as a host to construct a host–guest inclusion complex with xylene isomers, exhibiting self-adaptive structural behavior. Remarkably, para-xylene (pX) preferentially crystallizes with CHTA in a ternary xylene mixture, forming a pX-solvated structure. After desolvation, the resulting porous hydrogen-bonded organic framework (HOF) features a 1D channel, achieving selective pX adsorption from the simulated naphtha solution at a capacity of 103 mg/g. Even at a low concentration of pX (1%) in xylene isomers, the specific structure with pX occupancy in the channel is formed. The exceptional pX selective cocrystallization with CHTA and adsorption with desolvated HOFs enhance the development of pX adsorbents and extend the potential applications of HOFs.