Dong Bin, Wang Wen-Jing, Xi Sun-Chang, Wang Dong-Yue, Wang Ren
Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education, School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, 221116, P.R. China.
Chemistry. 2021 Feb 5;27(8):2692-2698. doi: 10.1002/chem.202003381. Epub 2021 Jan 12.
Instead of using organic solvents, a deep eutectic solvent (DES) composed of tetrabutylammonium bromide and imidazole (Bu NBr/Im) was employed as a solvent for the first time to synthesize covalent organic frameworks (COFs). Due to the low vapor pressure of the Bu NBr/Im-based DES, a new carboxyl-functionalized COF (TpPa-COOH) was synthesized under environmental pressure. The as-synthesized TpPa-COOH has open channels, and the DES can be removed completely from the pores. The dye adsorption performance of TpPa-COOH was examined for three organic dyes with similar molecular sizes: one anionic dye (eosin B, EB) and two cationic dyes (methylene blue, MB and safranine T, ST). TpPa-COOH showed an excellent selective adsorption effect on MB and ST. The electronegative keto form in TpPa-COOH might help to form electrostatic and π-π interactions between the π-stacking frameworks of TpPa-COOH and the positive plane MB and ST molecules. The adsorption isotherms of MB and ST on TpPa-COOH were further investigated in detail, and the equilibrium adsorption was well modeled by using a Langmuir isotherm model. Together with hydrogen bonding, TpPa-COOH showed higher adsorption capacity for ST than for MB (1135 vs. 410 mg g ). These results could provide a guidance for the green synthesis of adsorbents in removing organic dyes from wastewater.
首次使用由溴化四丁基铵和咪唑组成的低共熔溶剂（DES，即Bu₄NBr/Im）替代有机溶剂来合成共价有机框架（COF）。由于基于Bu₄NBr/Im的DES蒸气压低，在环境压力下合成了一种新型羧基官能化的COF（TpPa-COOH）。所合成的TpPa-COOH具有开放通道，且DES可从孔中完全去除。研究了TpPa-COOH对三种分子大小相似的有机染料的染料吸附性能：一种阴离子染料（曙红B，EB）和两种阳离子染料（亚甲基蓝，MB和番红花红T，ST）。TpPa-COOH对MB和ST表现出优异的选择性吸附效果。TpPa-COOH中的电负性酮形式可能有助于在TpPa-COOH的π堆积框架与带正电的平面MB和ST分子之间形成静电和π-π相互作用。进一步详细研究了MB和ST在TpPa-COOH上的吸附等温线，并用Langmuir等温线模型对平衡吸附进行了很好的模拟。连同氢键作用，TpPa-COOH对ST的吸附容量高于对MB的吸附容量（1135对410 mg g⁻¹）。这些结果可为从废水中去除有机染料的吸附剂绿色合成提供指导。
