Upcycling of waste poly(lactic acid) into crumped carbon nanosheet towards high-performance interfacial solar-driven evaporation

The controllable carbonization of waste plastics into functional carbon nanomaterials towards environmental remediation, energy conversion and storage has received widespread attention. However, there are few studies on the carbonization of poly(lactic acid) (PLA) into porous carbon. Herein, the controlled carbonization of PLA into crumped carbon nanosheet (CCN) is reported. Firstly, recycled PLA bags are converted into magnesium-based metal-organic framework (Mg-MOF) through the combined strategy of mechanochemical milling and solution mixing, and then Mg-MOF is transformed into CCN through the metal-organic framework (MOF)-assisted carbonization strategy. CCN exhibits merits of abundant nanopores and oxygen-containing groups. As a result, the CCN-derived evaporator holds good light absorptivity, low evaporation enthalpy, and good light-to-thermal conversion ability. Furthermore, the CCN-derived solar evaporator achieves a high evaporation rate (2.70 kg m-2 h-1) at 1 kW m-2 irradiation, along with good long-term stability, which surpasses many recent advanced solar evaporators. Noteworthy, when wastewater, lake water, seawater, tetracycline solution, and dye-polluted water are used, the CCN-based evaporator remains high performance in freshwater production. Importantly, an outdoor CCN-based device is constructed, which realizes the freshwater production of 6.3 kg m-2. The collected freshwater can cultivate well mung bean sprouts under natural condition. This work not only provides a new "turning-waste-into-treasure" method for the recycling of waste PLA, but also offers a novel strategy for the preparation of low-cost, functional carbon materials for diverse applications.