Smart ZIF-L mesh films with switchable superwettability synthesized via a rapid energy-saving process

Abstract

Smart materials with unique surface wetting properties have attracted considerable interest, particularly for oil/water separation, where oil can cause severe environmental damage. Despite 2 the considerable progress made in the past decade, critical challenges remain in scaling up, as smart materials are either expensive to fabricate or involve complicated, energy-intensive, and/or time-consuming production processes. In this work, an ultra-facile approach to fabricate hierarchical Zeolitic Imidazolate Framework-L (ZIF-L) mesh films with switchable superwettability for efficient oil/water separation was reported for the first time. A thick, continuous layer of well-intergrown ZIF-L nanoplates with an average aspect ratio of ~25 was successfully synthesized on various stainless steel (SS) meshes at ambient conditions. The ZIF-L mesh films exhibited extraordinary in-air superamphiphilic, underwater superoleophobic and underoil superhydrophobic properties, and showed outstanding performance in solely-gravitydriven oil/water mixture separation. Interestingly, a prewetting-induced switchable permeation function was found for the hierarchical ZIF-L surface, truly achieving "oil-blocking" and "water-blocking" separation. The ZIF-L mesh films demonstrated superior cyclic separation performance for a variety of oil/water mixtures with separation efficiencies above 99.99% and satisfactory chemical and mechanical stabilities even in harsh conditions. Their rapid and energy-efficient fabrication is therefore highly promising for cost-efficient and large-scale production for widespread applications in oil/water separation.

Facile fabrication of zeolitic imidazolate framework hollow fibre membranesviaa novel scalable continuous fluid circulation process

“…These results are consistent with those reported in one of our earlier studies. 46 Moreover, Fig 7c highlights the advantages of using ethanol during fabrication. The more ethanol (in the range of 0%10% V/V) was added, the higher water flux was observed, demonstrating further increased self-cleaning property and reduced fouling.…”

“…ZIF-L aqueous synthesis solutions were prepared as 55 mM Zn(NO 3 ) 2 •6H 2 O (aq) and 390 mM 2-methylimidazole (aq) (V:V =1:1) in accordance to our previous study. 46 Systematic adaptations were made to optimise the fabrications and separation performance tests (Fig. 1), including the use of ethanol during ZIF-L membrane fabrication (more details in ESI †).…”

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

“…20 Switchable wettability MOFs are smart materials, whose wettability can be switched between superhydrophobicity and superhydrophilicity or between underwater superoleophilicity and underwater superoleophobicity. 38,39,49 Superhydrophobic MOFs exhibiting superoleophilicity with OCA ¼ 0 are called superhydrophobic-superoleophilic MOFs. 50,51 The hydrophobicity of MOFs is an important property which can be achieved by four different strategies: (1) uorinated/ alkylated ligand-based MOF synthesis, (2) post-synthetic modi-cation of MOFs, (3) introduction of surface corrugations on MOFs, and (4) synthesis of composite hydrophobic MOFs.…”

“…For instance, when oil or water is used for tuning the wettability, the oil prewetted and water prewetted MOF materials exhibit super hydrophobicity and superoleophobicity, respectively. [38][39][40] This review summarizes recent developments and novel advances in the eld of hydrophobic-oleophilic, hydrophilic-underwater oleophobic and switchable wettability MOF materials. We discuss various MOFs and MOF-based oil/water separating materials by classifying them as ltration, absorbent or adsorbent materials.…”

A Fluoride‐Free and Super‐Wetting Functionalized‐Material with pH‐Responsiveness for Controllable Separation of Multiphase Oil/Water Mixtures

“…water-removing type [16,17] (usually shows superhydrophilicity/underwater superoleophobicity), and intelligent super-wetting materials. [18,19] Among them, the oil-removing type superwetting material is convenient to prepare and is a single oil-water separation material that is widely used. However, when it separates a low-density oil/water mixture, water will preferentially contact the surface of the separation membrane, thus preventing oil contact out of the separation film.…”