Synergism of solar-driven interfacial evaporation and photo-Fenton Cr(VI) reduction by sustainable Bi-MOF-based evaporator from waste polyester

The integration of interfacial solar steam generation and photocatalytic degradation technology has provided a promising platform to simultaneously produce freshwater and degrade pollutants. However, constructing low-cost, multi-functional evaporators for treating Cr(VI)-polluted water remains challenging, and the synergistic mechanism on Cr(VI) reduction is fuzzy. Herein, we propose the combined strategy of ball milling and solution mixing for the sustainable production of Bi-MOF microrod from waste poly(ethylene terephthalate), and construct Bi-MOF-based solar evaporators for simultaneous photo-Fenton Cr(VI) reduction and freshwater production. Firstly, the evaporator comprised of Bi-MOF microrod and graphene nanosheet possesses high light absorption, efficient photothermal conversion, and good hydrophilic property. Attributing to the advantages, the hybrid evaporator exhibits the evaporation rate of 2.16 kg m−2 h−1 and evaporation efficiency of 87.5% under 1 kW m−2 of irradiation. When integrating with photo-Fenton reaction, the Cr(VI) reduction efficiency is 91.3%, along with the reaction kinetics of 0.0548 min−1, surpassing many advanced catalysts. In the outdoor freshwater production and Cr(VI) reduction, the daily accumulative water yield is 5.17 kg m−2 h−1, and the Cr(VI) reduction efficiency is 99.9%. Furthermore, we prove that the localization effect derived from the interfacial solar-driven evaporation enhances H2O2 activation for the photo-Fenton reduction of Cr(VI). Based on the result of density functional theory, Bi-MOF microrod provides rich active centers for H2O2 activation to produce active sites such as e− or ·O2−. This study not only proposes a new strategy to construct multi-functional solar evaporators for freshwater production and catalytic reduction of pollutants, but also advances the chemical upcycling of waste polyesters.