Evaluating the Effect of Resorcin[4]Arenes Conformational Structures on the Remediation of Methylene Blue in Water

In this study, the effects of resorcin[4]arenes/cavitand structural properties: (i) hydrophobicity, aliphatic alkyl tails elongation (methyl, propyl, hexyl, and nonyl) based on macrocycles <b>1-4</b> lower rims; (ii) H-bond and dipole-dipole importance, resorcin[4]arene <b>4</b> vs its rigid core structure cavitand <b>5</b>; and (iii) cavity order/disorder, crown (<i>C</i> _4v) <b>4</b> vs chair (<i>C</i> _2h) <b>6</b> isomers on the remediation of methylene blue (MB) in water have been investigated. Additionally, the adsorption kinetics/isotherms of MB by octols <b>1-4</b> were studied, indicating that the adsorption process follows <i>pseudo</i>-second order and Langmuir models, respectively. Notably, the longest alkylated crown (<i>C</i> _4V) conformer <b>4</b> was found to be the best adsorbent among the studied macrocycle family with a remarkable adsorption capacity (<i>Q</i> _max = 769.230 mg/g), owing to its unique structural features and tail-to-tail aggregation behavior in water. Hence, resorcin[4]arene <b>4</b> was further used to evaluate its adsorption efficiency toward other (non)ionic dyes, and the results were considerable. Also, its recoverability/reusability toward MB removal from water was examined for five consecutive cycles, and the results revealed a promising recovering capability with excellent adsorption efficiency, leading to confidence in its effective use for manifold adsorption/desorption cycles.