Tuning the Wettability of Metal–Organic Frameworks via Defect Engineering for Efficient Oil/Water Separation

Abstract

Zirconium-based metal–organic frameworks (MOFs) have attracted interest due to their chemical and thermal stabilities and structural tunability. In this work, we demonstrate the tuning of the wettability of a UiO-66 structure via defect-engineering for efficient oil/water separation. UiO-66 crystals with controlled levels of missing-linker defects were synthesized using a modulation approach. As a result, the hydrophilicity of the defect-engineered UiO-66 (d-UiO-66) can be varied. In addition, a thin layer of hydrophilic d-UiO-66 was successfully fabricated on a series of stainless steel meshes (d-UiO-66@mesh), which exhibited excellent superhydrophilic and underwater superoleophobic properties and displayed interesting separation performance for various oil/water mixtures.

Synthesis, characterization and application of defective metal–organic frameworks: current status and perspectives

“…Defective sites in MOFs have been used to tune the hydrophilicity and wettability. 105,106 It has also been reported that water adsorption measurements can be a complementary tool to analyze the defects in Zr-MOF. 87,107 Two simple but important parameters, Henry constant (the slope of the adsorption pressure in the low pressure range) and the saturation water uptake quantitatively represent the defect-induced hydrophilicity, which can be used to predict the catalytic properties for Lewis acid-based reactions.…”

Tuning the Properties of MOF‐808 via Defect Engineering and Metal Nanoparticle Encapsulation

“…The increased accessibility of metal sites as the linkers are removed has been proposed as the mechanism at the origin of these improvements [21, 22] . More recently, the tuning of the hydrophilicity of MOF crystals via defect engineering for efficient oil/water separation has been demonstrated in Zr‐based UiO‐66 [23] . The enhancement in catalytic activity has also been achieved by preparing a so‐called “composite MOF” or “metal@MOF” by metal impregnation [24] or metal encapsulation [25, 26] .…”

Hierarchical porous metal–organic framework materials for efficient oil–water separation

“…Recently, inspired by the structural stability and tunability of the UiO-66 MOF, Huang et al increased the hydrophilicity of UiO-66 by incorporating absent-linker defects into its structure. 157 The defect framework of UiO-66 (d-UiO-66) was obtained by adding acetic acid to the reaction mixture, which competes with H 2 BDC for participating in UiO-66 synthesis. In d-UiO-66, some of the H 2 BDC linkers were replaced by acetate ions, while the terminal -OH groups balance the positive charge of the metal ion.…”

“…Reproduced with permission. 157 Copyright 2020, American Chemical Society. (e) Separation parameters of UiO-66-coated membranes for various oil-water mixtures.…”

“…(d) Stability of the oil/water separation performance of UiO-66@mesh-400. Reproduced with permission 157. Copyright 2020, American Chemical Society.…”