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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. [Display omitted] • Mg-MOF with daisy-like morphology is prepared from waste PLA bags in a green manner. • Carbon nanosheet with a thickness of 2.5 nm is obtained by carbonization of Mg-MOF. • The carbon nanosheet-based evaporator effectively realizes freshwater production. • Evaporator shows the evaporation rate of 2.71 kg m−2 h−1 with efficiency of 98.6%. • This work provides a new "turning-waste-into-treasure" strategy for PLA recycling. [ABSTRACT FROM AUTHOR]

Interfacial solar-driven water evaporation is an appealing technology to mitigate freshwater crisis mainly caused by increasingly aggravated water pollution. Unfortunately, when polluted water is used, toxic organic pollutants might remain or even get enriched, leading to more serious water pollution. Herein, a self-floating bifunctional Fe 2 O 3 /N,O-doped carbon foam (FCF) evaporator is easily prepared by carbonization of waste polyester for simultaneous interfacial solar-driven water production and photocatalytic degradation of organic pollutants. The as-prepared FCF possesses low heat conductivity (0.074 W m−1 K−1), 3D interconnected pores, abundant functional groups as well as super-hydrophilicity, which impart FCF with fast water transport, high light absorptivity (98%), good photothermal conversion, and low vaporization enthalpy. Therefore, FCF presents high evaporation performance, e.g., 2.50 kg m−2 h−1 under 1 Sun irradiation, outperforming many advanced solar evaporators. Furthermore, the synergistic effect of heteroatom-doped carbon foam, Fe 2 O 3 nanoparticle, and interfacial thermal energy is certified on the activation of peroxymonosulfate (PMS) to form diverse reactive oxide species (e.g., SO 4 •−), which promote the degradation of diverse organic dyes or mixed dyes. Compared with FCF and PMS systems, the rate constant of FCF + PMS system (3.79 ×10−2 min−1) is enhanced by 173.8 and 1.6 times, respectively. In outdoor experiments, the amount of freshwater production from per meter square (13 kg) satisfies with 5 adults' daily water demand, and the dye degradation efficiency reaches 99.8%. The integration of advanced oxidation process into interfacial solar evaporation offers a promising strategy to simultaneously solve freshwater scarcity and sewage disposal. [Display omitted] • A bifunctional Fe 2 O 3 /N,O-doped carbon foam evaporator is prepared from waste bottle. • FCF owns high light absorbance/photothermal conversion and low evaporation enthalpy. • FCF exhibits a high evaporation rate of 2.5 kg m−2 h−1 with the efficiency of 87.2%. • FCF and interfacial heat energy synergistically activate PMS for dye degradation. • The outdoor freshwater production satisfies with five adults' daily water demand. [ABSTRACT FROM AUTHOR]