Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal-Organic Framework Architectures

The rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar-like Co-CAT-1 metal-organic framework (MOF) crystallites on gold-coated woven stainless steel meshes with large, 50 mu m apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity-driven, highly efficient oil-water separation featuring water fluxes of up to nearly one million L m(-2) h(-1). Water physisorption experiments reveal the hydrophilic nature of Co-CAT-1 with a total water vapor uptake at room temperature of 470 cm(3) g(-1). Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF-based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L-1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on-surface extreme wetting properties, yielding energy-efficient water-selective large-aperture membranes.

Automated summary

This study presents a unique nanoscale material that enables efficient oil-water separation driven by gravity, with high water flux and water adsorption capacity. Furthermore, the material exhibits high separation efficiency for various liquids, particularly in treating water pollutants such as crude oil.