Tan Wei, Wu Xiaohai, Liu Wenren, Ye Fanggui, Zhao Shulin
State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmaceutical Science, Guangxi Normal University, Guilin 541004, P. R. China.
Department of Food and Chemical Engineering, Liuzhou Institute of Technology, Liuzhou 545616, P. R. China.
ACS Appl Mater Interfaces. 2021 Jan 27;13(3):4352-4363. doi: 10.1021/acsami.0c18902. Epub 2021 Jan 12.
Pore size and functionalization are two critical factors for covalent organic frameworks (COFs) as effective adsorbents. However, due to the low crystallinity of COFs, it is a grand challenge to accomplish pore diameter adjustment and functionalization at the same time. In this work, we developed a simple and ingenious strategy, cutting off linkage, to synchronously construct hierarchical porosity and modify thiol groups in COFs under mild conditions. The hybrid COFs containing disulfide bonds were designed and synthesized, and then the disulfide bonds were cleaved by glutathione, resulting in the formation of thiol groups as well as the increase in pore size caused by skeleton defects. The pore diameter of thiol-functionalized hierarchical porous COFs (denoted as HP-TpEDA-SH) was concentrated at 2.6 and 3.5 nm. Thanks to the electrostatic attraction of thiol groups to cationic dyes and the higher number of available adsorption sites, the maximum extraction amounts of methylene blue (MB), malachite green (MG), and crystal violet (CV) by HP-TpEDA-SH were 2.6, 2.1, and 3.3 times those of microporous COFs under optimal extraction conditions, respectively. The proposed analytical method (solid-phase extraction-high-performance liquid chromatography/ultraviolet (SPE-HPLC/UV)) with HP-TpEDA-SH as the adsorbent showed low detection limits of 1.3, 0.13, and 0.12 μg·L for MB, MG, and CV, respectively. The recoveries of three spiked water samples ranged from 81.5 to 113.8%, with relative standard deviations (RSDs) less than 9.7%. This work not only opened a new avenue for the preparation of functionalized hierarchical porous COFs but also established an effective method for detecting trace cationic dyes in fishery water.
孔径和功能化是共价有机框架材料（COFs）作为有效吸附剂的两个关键因素。然而，由于COFs的结晶度较低，要同时实现孔径调节和功能化是一项巨大的挑战。在这项工作中，我们开发了一种简单而巧妙的策略——切断连接，在温和条件下同步构建COFs的分级孔隙结构并修饰硫醇基团。设计并合成了含有二硫键的杂化COFs，然后通过谷胱甘肽裂解二硫键，形成硫醇基团，同时由于骨架缺陷导致孔径增大。硫醇功能化分级多孔COFs（记为HP-TpEDA-SH）的孔径集中在2.6和3.5 nm。由于硫醇基团对阳离子染料的静电吸引以及更多的可用吸附位点，在最佳萃取条件下，HP-TpEDA-SH对亚甲基蓝（MB）、孔雀石绿（MG）和结晶紫（CV）的最大萃取量分别是微孔COFs的2.6倍、2.1倍和3.3倍。以HP-TpEDA-SH为吸附剂的所提出的分析方法（固相萃取-高效液相色谱/紫外检测法（SPE-HPLC/UV））对MB、MG和CV的检测限分别低至1.3、0.13和0.12 μg·L。三个加标水样的回收率在81.5%至113.8%之间，相对标准偏差（RSDs）小于9.7%。这项工作不仅为制备功能化分级多孔COFs开辟了一条新途径，还建立了一种检测渔业水中痕量阳离子染料的有效方法。
