Oily wastewater and oil

spills not only cause large amounts of resource wastefulness,

but threaten water safety and human health. Besides, for some oily

emulsions, the oil droplets are usually valuable, such as the soybean

oil droplets formed during oil manufacture, and

the oil droplets carrying high valued product from

the extraction process or micro-emulsion reactor. Therefore, the

collection and recovery of oil

from water are particularly important.

However, the recovery of oil droplets form emulsions and collection-lossless

transportation of oil spills are still a big challenge, which cannot be solved

by current oil/water separation methods, including the super-wetting strategy. Herein,

we designed and prepared oil-unidirectional Janus membrane via unilateral

decoration of commercial hydrophobic composite microfiltration membranes. The

obtained Janus membrane is composed of a thin hydrophilic layer and thick

hydrophobic supporting layer, and the asymmetric surface wettability can

realize the unidirectional oil-transport property, viz. oil “diode”. Therefore,

the obtained JMs with oil unidirectional transport property can realize the

efficient collection and recovery of various oils. For example, the JM can

effectively draw the micrometer-sized oil droplets from various oil-in-water

emulsions, and realize the collection-lossless

transportation of the oil spills. Our strategy can firmly stimulate

and accelerate the advances of functional membranes toward the broad

intelligent and sustainable usages.