Superwetting Oil/Water Separation Membrane Constructed from In Situ Assembled Metal–Phenolic Networks and Metal–Organic Frameworks

Abstract

Superwetting membranes with opposite wettability to oil and water have drawn intense attention in recent years for oil/water separation. Superhydrophilic and underwater superoleophobic membranes have shown unique advantages in the efficient treatment of oily wastewater containing oil-in-water emulsions. Facile interfacial engineering and microstructural design of the hierarchical architectures and the hydrophilic chemistry is of significance but still challenging. In this study, a hydrophilic hierarchical hybrid layer derived from metal−phenolic network (MPN)/metal−organic framework (MOF) synergy is constructed on the membrane surface via a proposed coordination-directed alternating assembly strategy. The assembly of MPN multilayers provides a hydrophilic chemical basis, and the assembly of MOF nanocrystals provides a hierarchical structural basis. Notably, the coordination interfacial interaction enables the formation of well-defined hydrophilic hierarchical architectures. The obtained membrane is thus endowed with robust superhydrophilicity, underwater superoleophobicity, and anti-oil-adhesion capability, which make it capable of highly efficient oil− water separation with high water permeance (above 6300 L/m 2 h), high oil rejection (above 99.4%), and recyclable antifouling property. The high performance of the developed superwetting membrane makes it a competitive candidate for oil/water separation. Additionally, the demonstrated MPN/MOF assembly strategy may offer new prospects for the facile and versatile design of other superwetting materials.

Recent advances in membrane hydrophilic modification with plant polyphenol‐inspired coatings for enhanced oily emulsion separation

“…Both metal‐phenolic networks (MPN) and metal organic frameworks (MOFs) are promising and prominent materials based on metal–organic coordination 101 . In the work by Wang et al, 75 MPN/MOFs synergy was constructed on membrane surface combining the multilayer assembly of hydrophilic TA‐Ti 4+ network and the in‐situ assembly of zeolitic imidazolate framework‐8 (ZIF‐8) nanocrystals, as shown in Figure 11. Of note, the TA‐Ti 4+ primer layer manipulated even distribution of the generated ZIF‐8 nanocrystals, as the unreacted catechol groups of TA could capture and chelate with Zn 2+ ions to facilitate heterogeneous MOF nucleation 102 .…”

“…(a) Schematic illustration of the coordination‐directed alternating assembly strategy via the synergy of TTN multilayers and ZIF nanocrystals; (b) surface SEM images of the pristine PVDF, TTN (Ti 4+ ‐tannic acid network)@PVDF, ZIF‐TTN@PVDF, and TTN‐ZIF‐TTN@PVDF membranes. Copyrights obtained from American chemical Society 75 [Color figure can be viewed at wileyonlinelibrary.com]…”

Superwettable PVDF/PVDF-g-PEGMA Ultrafiltration Membranes

“… 23 , 24 Each model has its own applicabilities and limitations. 25 When studying the physicochemical properties of the membrane surface, the extended DLVO (XDLVO) theory can be applied to determine interfacial tensions and free energies. 20 , 21 These theories and models can provide a rationalization for the wetting behavior of the membrane surfaces, before and after modification or functionalization.…”

Porous Membranes with Special Wettabilities: Designed Fabrication and Emerging Application

“…11,12,39,40 In addition, MOF membranes can be fabricated on various substrates via the solvothermal crystallization process, [41][42][43] or by embedding the as-prepared MOF particles into graphite oxides, [44][45][46] fabrics, 47,48 and polymer-based matrixes. [49][50][51][52][53][54][55] For example, ZIF-8 is a well-known zeolite imidazole framework (ZIF) with exceptional hydrothermal and chemical stability, composed of Zn metal centers coordinated by four 2-methylimidazolate (MIM) molecules. 56 The nanosized ZIF-8 crystals can be inserted between fluorinated graphene oxide sheets, 44,46 or grafted onto the melamine sponges 53,54 or carbon nitride foams, 57 achieving excellent superhydrophobicity along with superoleophilicity, which could adsorb various organic pollutants from oily wastewater.…”