Xiaochang Lin,Bo Sun,Pengsen Wang,Min Zhao,Dejia Liu,Qiyu Zhang,Baile Wu,Dezhao Liu
A magnetic Fe n UiO-66 adsorbent was created to achieve high phosphate adsorption capacity. The incorporation of Fe 3 O 4 facilitated the precipitation and growth of UiO-66 during crystallization, resulting in a shift towards a multilayer heterogeneous distribution of adsorption sites. The increased Fe 3 O 4 content notably enhanced the magnetic properties of Fe n UiO-66, while negligibly affecting its adsorption performance. The Fe 1.5 UiO-66 demonstrated exceptional phosphate adsorption capacity (136.54 mg/g), outstanding selectivity, and sustained reusability, with an 80% removal efficiency after nine cycles of treating actual water. The mechanism of phosphate adsorption by Fe n UiO-66 involved electrostatic attraction, ligand exchange, and linker exchange. Notably, while linker exchange significantly contributed to high adsorption capacity, it resulted in irreversible damage to the Fe n UiO-66 crystal. These unequivocal findings will serve as a solid foundation for further research and underline the critical role of linkers in the process of phosphate adsorption.
Metal organic framework (MOF) membranes have exhibited great potential for efficient gas separation owing to their excellent chemical and structural tunability. To realize CO 2 separation from flue gas, linker modification or exchange is generally required to functionalize MOF membranes. However, the reported linker-exchanged polycrystalline MOF membranes have not yet achieved attractive CO 2 separation performance due to the sacrificed permeance of the overly reduced pore apertures when employing bulky linkers. Herein, we report a 3-amino-1,2,4-triazole (Atz)-exchanged polycrystalline ZIF-8 membrane (Atz-ZIF-8) with Atz molar ratios ranging from 3% to 29% which shows an excellent CO 2 /N 2 separation performance that significantly surpasses that of other linker-exchanged ZIF-8 membranes. The as-synthesized Atz-ZIF-8 membranes possess additional uncoordinated amines for CO 2 -preferential adsorption, resulting in an excellent CO 2 /N 2 selectivity of 29. What's more, the size and configuration of Atz is similar to 2-methylimidazole (2-mIm), so the window size of Atz-ZIF-8 membranes is not significantly reduced, and thus high CO 2 permeance (690 GPU) is achieved. Considering the superior performance and accessible manufacturing process, we conclude that our work could provide guidelines on designing advanced linker-exchanged ZIF-8 based polycrystalline membranes towards post-combustion carbon capture.
Covalent organic frameworks (COFs) have gained tremendous interest as membrane building blocks owing to rigid, long-range ordered and easily functionalized skeletons. The facile, controllable and task-specific construction of COF membranes lies in the frontier of membrane technology . Herein, we explored a post-synthetic linker exchange (PLE) method to engineer COF membranes for efficient alcohol dehydration. The proposed PLE method, utilizing the reversible breaking-reformation basis between pristine COF membranes and post-introduced linkers, narrowed the effective pore size to intensify molecular sieving property. Moreover, the PLE method also endowed COF membranes with more hydrophilic groups, thus improving the water sorption ability of COF membranes. The resultant COF membranes exhibited superior n -butanol dehydration performances with 3620 of selectivity, 11.35 kg m −2 h −1 of total flux and remained stable in 15-day operation. This PLE method may flourish the library of engineering COF membranes for efficient molecular separations.
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