Self-assembly of rare-earth Anderson polyoxometalates on the surface of imide polymeric hollow fiber membranes potentially for organic pollutant degradation

• The POMs-functionalized membranes were constructed by a simple self-assembly method.
• The self-assembled POMs nanoparticles are crystalline with the size of around 50 nm.
• Catalytic degradation of phenol in water has been achieved under mild conditions.
• A gas–catalyst–liquid interface was built up to enhance the catalytic efficiency.

In this study, the self-assembly of rare-earth Anderson polyoxometalates (POMs) on the surfaces of imide polymeric hollow fiber membranes was designed for fabrication of novel POMs-functionalized interfacial composite membranes. The rare-earth Anderson POM ([Gd(H2O)7Cr(OH)6Mo6O18]n) nanoparticles with controllable size and distribution were successfully constructed. Experimental results revealed that the self-assembly was a surface-induced growth process. The silanol groups on the membrane surfaces generated by the (3-aminopropyl)trimethoxysilane pretreatment were essential for the self-assembly process because of the potential hydrogen bonding (OH⋯POMs) and coordination bonding (OHGd) interactions. This work provided a simple but practical method not only for the fabrication of novel POMs-functionalized membranes, but also for the synthesis of POMs nanoarchitectures. In addition, the potential application of the as-prepared POMs-functionalized hollow fiber membranes in degradation of organic pollutant has also been explored. The idea of interfacial membrane contactor has been utilized for the catalytic wet air oxidation of phenol under mild conditions. A three-phase (gas/catalyst/liquid) interface was successfully built up, which enhanced the catalytic efficiency. It is anticipated that these novel POMs-functionalized membranes can promisingly be used as catalytic membrane contactors for wastewater treatment under mild conditions.