Cucurbit[8]uril-mediated efficient separation of o-nitrotoluene from nitrotoluene isomers

Nitrotoluene isomers are vital chemical intermediates, but their separation is challenging due to similar properties. This work introduces a supramolecular strategy using cucurbit[8]uril (Q[8]) to selectively isolate ortho-nitrotoluene (ONT). Through methods including single-crystal XRD, ITC, GC, and theoretical calculations, host–guest interactions in formic acid were characterized. Gradient solvent volatilization of Q[8] with isomer mixtures enabled controlled crystallization. Results show Q[8] strongly prefers ONT, with binding constants of 3.628×10⁶ M⁻¹ (ortho) vs. 8.712×10⁵ M⁻¹ (meta) and 2.173×10⁵ M⁻¹ (para), giving selectivity ratios of 4.16 and 13.37, respectively. Crystal structures reveal stabilization via π–π stacking and hydrogen-bonding networks. These interactions drive multidimensional assembly into ordered architectures through synergistic surface interactions, hydrogen bonding, and aromatic stacking. This work extends cucurbituril applications in adsorption and separation.