CuMOF functionalized PVDF membrane with hierarchical structure for photothermal vacuum membrane distillation

One of the most promising desalination techniques is photothermal membrane distillation (PhMD). The research focus of PhMD technology is material renewal and structural design. Herein, the CuMOF-PVDF photothermal membranes were designed for PhMD. Firstly, a combination of chemical plating and oxidation was used to generate Cu(OH)2 nanowires (NWs) onto the PVDF membrane. Then, the ligands were chemically bonded with Cu(OH)2 NWs to grow the photothermal layer formed by the CuMOF hierarchical structure (CMHS). Under sunlight irradiation, the light was trapped in the CMHS, amplifying absorption and conversion of light. The CuMOF-PVDF membrane with the match-like CMHS absorbed 88.6% of the light, resulting in a surface temperature of 74.3°C after 600s. Moreover, by reducing the evaporation enthalpy of water, the performance of the CuMOF photothermal layer was comprehensively improved, realizing a water evaporation rate of 1.55 kg‧m-2‧h-1 and a high photothermal conversion rate of 71.4%. During the PVMD process, the feed solution in the CuMOF photothermal layer was fully heated and supplied to the vaporization area, weakening the temperature polarization. Consequently, the flux of the CuMOF-PVDF membrane was 3.07 kg‧m-2‧h-1 and a 99.9% rejection rate, corresponding to an energy efficiency of 85.2%. The CuMOF-PVDF membrane is an efficient tool for PhMD, helping to advance desalination technologies.