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

Smart materials with unique surface wetting properties have attracted considerable interest, particularly for oil/water separation, where oil can cause severe environmental damage. Despite 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-gravity-driven 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.