Li Xiaoting, Wang Yanlei, Chang Jian, Sun Hao, He Hongyan, Qian Cheng, Kheirabad Atefeh Khorsand, An Quan-Fu, Wang Naixin, Zhang Miao, Yuan Jiayin
Beijing Key Laboratory for Green Catalysis and Separation, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, P. R. China.
Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden.
ACS Nano. 2021 Mar 23;15(3):4440-4449. doi: 10.1021/acsnano.0c08308. Epub 2021 Feb 15.
Assembling two-dimensional (2D) materials by polyelectrolyte often suffers from inhomogeneous microstructures due to the conventional mixing-and-simultaneous-complexation procedure ("mix-and-complex") in aqueous solution. Herein a "mix-then-on-demand-complex" concept on-demand cascade anionization and ionic complexation of 2D materials is raised that drastically improves structural order in 2D assemblies, as exemplified by classical graphene oxide (GO)-based ultrathin membranes. Specifically, in dimethyl sulfoxide, the carboxylic acid-functionalized GO sheets (COOH-GOs) were mixed evenly with a cationic poly(ionic liquid) (PIL) and upon filtration formed a well-ordered layered composite membrane with homogeneous distribution of PIL chains in it; next, whenever needed, it was alkali-treated to convert COOH-GO into its anionized state COO-GO that immediately complexed ionically with the surrounding cationic PIL chains. This "mix-then-on-demand-complex" concept separates the ionic complexation of GO and polyelectrolytes from their mixing step. By synergistically combining the PIL-induced hydrophobic confinement effect and supramolecular interactions, the as-fabricated nanofiltration membranes carry interface transport nanochannels between GO and PIL, reaching a high water permeability of 96.38 L m h bar at a maintained excellent dye rejection 99.79% for 150 h, exceeding the state-of-the-art GO-based hybrid membranes. The molecular dynamics simulations support the experimental data, confirming the interface spacing between GO and PIL as the water transport channels.
由于在水溶液中采用传统的混合并同时络合程序（“混合-络合”），通过聚电解质组装二维（2D）材料常常会出现微观结构不均匀的问题。在此，我们提出了一种“先混合后按需络合”的概念，即对二维材料进行按需级联阴离子化和离子络合，这极大地改善了二维组装体中的结构有序性，以经典的基于氧化石墨烯（GO）的超薄膜为例。具体而言，在二甲基亚砜中，将羧酸功能化的氧化石墨烯片（COOH-GOs）与阳离子聚离子液体（PIL）均匀混合，过滤后形成了一种结构有序的层状复合膜，其中PIL链均匀分布；接下来，在需要时，对其进行碱处理，将COOH-GO转化为其阴离子化状态COO-GO，后者立即与周围的阳离子PIL链发生离子络合。这种“先混合后按需络合”的概念将GO与聚电解质的离子络合与其混合步骤分开。通过协同结合PIL诱导的疏水限制效应和超分子相互作用，所制备的纳滤膜在GO和PIL之间携带界面传输纳米通道，在150小时内保持99.79%的优异染料截留率的同时，实现了96.38 L m⁻² h⁻¹ bar⁻¹的高水渗透率，超过了基于GO的最先进的混合膜。分子动力学模拟支持了实验数据，证实了GO和PIL之间的界面间距为水传输通道。
