Enhanced selective adsorption of benzotriazole onto nanosized zeolitic imidazolate frameworks confined in polystyrene anion exchanger

•New nanocomposite adsorbent ZIF-67/D201 is prepared by an alternate deposition method.•ZIF-67/D201 exhibits enhanced adsorption capacity to BTA.•ZIF-67/D201 has selective affinity to BTA when BTA with similar structure coexists.•Density functional theory (DFT) calculation is used to clarify adsorption mechanism.•A strategy for precise separation of pollutants with similar structure is provided.

A new nanocomposite adsorbent ZIF-67/D201, in which nanocrystalline ZIF-67 were immobilized inside the networking pores of a commercial polystyrene anion exchanger D201 by an alternate deposition method, with high capacity and enhanced selective affinity toward benzotriazole (BTA) was fabricated and characterized. ZIF-67/D201 demonstrated precise selective adsorption of BTA when benzimidazole (BMA), with very similar chemical structure to BTA, coexisted. After the uptake of BTA, ZIF-67/D201 could be regenerated for repeated use with slight capacity loss. According to kinetics data, two diffusion steps driven by electrostatic attraction were found prior to adsorption equilibrium: a fast diffusion of the contaminant into mesopores of D201 and then a relatively slow diffusion into micropores of ZIF-67. The underlying mechanism for the enhanced selective adsorption was revealed by spectral analysis and density functional theory (DFT) calculations. Three sorts of interactions (coordination, electrostatic attraction and π-π interaction) contributed to the fixing of contaminants. Among them, coordination was the predominant effect. For each sort of interaction, the binding energy of adsorbent-BTA was always larger than that of adsorbent-BMA, which was the intrinsic reason of the high selectivity in molecular level. The above results provided a strategy for precise separation of components with similar structures in water.

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