Ion-exchange is one of the most efficient methods for removal of water pollutants, like hexavalent chromium (Cr(VI)). Herein, we report the preparation and application of a family of hypercrosslinked imidazolium-based poly(ionic liquid)s (PILs) with different crosslinker lengths, ion contents, and textural properties. We discover the hypercrosslinking porous structure and the anion content (corresponding to the theoretical adsorption capacity) of PILs play decisive roles in their capture capacities towards Cr(VI). Among them, PVIm-6-SCD prepared by free-radical polymerization of monomer with higher anion content and subsequent supercritical CO₂ drying (SCD) displays excellent textural properties such as abundant mesoporous structure, high surface area and large pore volume. It facilitates the exposure of high density of exchangeable Br⁻ in PVIm-6-SCD, thereby speed up the mass transfer during ion-exchange for Cr(VI). It shows a high utilization of the adsorption sites (84.5%) and a very high Cr(VI) adsorption capacity (236.8 mg·g⁻¹, 25 °C), which is much higher than those of the literature reported adsorbents. Remarkably, PVIm-6-SCD exhibits good selectivity for Cr(VI) in the presence of competing anions including chloride (Cl⁻), nitrate (NO₃⁻), dihydrogen phosphate (H₂PO₄⁻), and sulphate (SO₄²⁻). Moreover, it is effective for Cr(VI) removal under a broad range of pH (2–12). Besides, it has good reusability, showing potential industrial application prospects. This work highlights the PILs with high density of ion pairs for application in wastewater treatment.

离子交换是去除水污染物（如六价铬（Cr（VI）））的最有效方法之一。在本文中，我们报告了具有不同交联剂长度，离子含量和质构性质的超交联咪唑基聚（离子液体）家族的制备和应用。我们发现超交联的多孔结构和PILs的阴离子含量（对应于理论吸附容量）在其对Cr（VI）的捕获容量中起决定性作用。其中，通过自由基聚合具有较高阴离子含量的单体和随后的超临界CO ₂制备的PVIm-6-SCD干燥（SCD）显示出优异的质地特性，例如丰富的中孔结构，高表面积和大孔体积。它便于更换的Br与高密度的曝光^-在PVIm-6-SCD，从而加快离子交换为铬（VI）时的质量传递。它显示了吸附位（84.5％）和非常高的铬（VI）吸附容量（236.8毫克·g的高利用率^-1，25℃），它是比那些文献的高得多的报道吸附剂。值得注意的是，PVIm-6-SCD表现出对Cr在竞争阴离子的存在良好的选择性（VI），包括氯化（氯^{- ），}硝酸根（NO ₃ ^- ），磷酸二氢（H ₂ PO₄ ^- ），和硫酸盐（SO ₄ ^2-）。此外，它在宽范围的pH值（2–12）下对于去除Cr（VI）都是有效的。此外，它具有良好的可重用性，显示出潜在的工业应用前景。这项工作重点介绍了用于废水处理的具有高密度离子对的PIL。