Near-Perfect Separation of Aromatic and Cyclic Aliphatic Hydrocarbons Using Amorphous Cucurbit[7]uril

Cyclic aliphatic compounds and their corresponding aromatic counterparts possess similar physical properties, making their separation a significant challenge. Conventional isolation techniques are hampered by significant energy expenditure, intricate operation, and inefficiency, especially when separating compounds with comparable boiling points. This paper introduces an innovative approach using amorphous cucurbit[7]uril (Q[7]) for the separation of aromatic and cyclic aliphatic compounds by leveraging the differential strength of weak hydrogen-bonding interactions. Q[7] can selectively capture toluene (Tol) from a Tol and methylcyclohexane (MCH) mixture, achieving 100% selectivity at the solid–vapor interface and 98.82% at the solid–liquid interface. It can also selectively capture chlorobenzene (CB) from a CB/chlorocyclohexane (CCH) mixture, with selectivity reaching 100% in both solid–vapor and solid–liquid interfaces. The kinetic experiment results demonstrate that the adsorption behaviors of Tol and CB align precisely with the pseudo-second-order model. Calculations based on density functional theory (DFT) indicate that the selectivity arises from the enhanced structural stability conferred upon Q[7] after it adsorbs the preferred guest molecules. Furthermore, amorphous Q[7] can be reused without loss of selectivity or performance, underscoring its potential in sustainable chemical separation processes.