Waste cigarette butts based super-hygroscopic photothermal materials for atmospheric water harvesting and solar-driven undrinkable water purification

The worsening of the freshwater crisis undoubtedly poses great challenges to the normal production and life of human beings. Developing multifunctional materials that are capable of both atmospheric water harvesting and undrinkable water purification is highly desirable for freshwater production but is rare. In this study, a super-hygroscopic photothermal material (WCBs@SA/MNPs/MOFs) composed of environmentally polluting waste cigarette butts (WCBs), sodium alginate (SA), metal–organic framework-Zr (MOF-801) and melanin nanoparticles (MNPs) was successfully fabricated. Benefiting from the simultaneous loading of moisture-absorbing MOF-801 and photothermal MNPs into the porous structure of WCBs, freshwater production consisting of efficient atmospheric water harvesting (daily water production of ∼ 1.41 L kg −1 at low relative humidity of 20 % and 5.42 L kg −1 at higher relative humidity of 80 %, respectively) and eco-friendly solar-driven undrinkable water purification (water evaporation rate ∼ 2.72 kg m -2 h −1 , 1 kW m −2 ) can be realized concurrently. We believe this research not only mitigates environmental pollution caused by discarded cigarette butts and enhances their economic value, but also expands the options for freshwater production with multiple positive implications.