Functional upcycling of waste polyester into Cr-MOF towards synergistic interfacial solar evaporation and organic pollutant degradation

The development of hybrid photothermal materials coupling interfacial solar-driven water evaporation with advanced oxidation process has recently aroused extensive attention to simultaneously realize freshwater production and wastewater purification. However, designing advanced hybrid photothermal materials with high specific surface areas and robust active sites remains challenging to meet the distinct requirements of photothermal conversion and photocatalysis. Herein, we report the waste-to-MOF strategy for converting waste poly(ethylene terephthalate) into Cr-MOF hexahedron with abundant active sites and large specific surface area (896.1 m2 g-1), and subsequently fabricate multi-functional Cr-MOF/carbon nanotube composite solar evaporators in a cost-effective, scalable manner towards simultaneous interfacial solar-driven steam generation and stubborn contaminant removal. Firstly, the composite evaporator presents high light absorption (98%), high photothermal conversion efficiency, super-hydrophilicity, low thermal coefficient (0.087 W m-1 K-1) and low vaporization enthalpy. Accordingly, the composite evaporator not only holds a high evaporation rate (2.46 kg m-2 h-1), superior to most of advanced solar evaporators, but also owns good flexibility and long-term stability. Subsequently, according to density functional theory calculation and COMSOL results, chromium sites of Cr-MOF and local solar heat contribute to the peroxymonosulfate activation to produce various reactive species. Thereupon, the composite evaporator exhibits good tetracycline degradation activity. Finally, in the practical freshwater production and photocatalytic degradation, the freshwater production amount is 7.3 kg m-2 per day, along with the tetracycline degradation efficiency of 92.4%. This work provides an ingenious strategy to massively synthesize hybrid evaporators and concurrently advances freshwater production and pollutant elimination.