Universal Strategy to Prepare a Flexible Photothermal Absorber Based on Hierarchical Fe-MOF-74 toward Highly Efficient Solar Interfacial Seawater Desalination

Solar-driven interfacial steam generation (SDISG), as an emerging green and renewable approach to overcome water shortage, is very suitable for remote locations, developing countries, and disaster zones because it does not require an additional energy supply. However, the traditional metal-based and carbon-based absorbers always suffered from fragility (or rigidity) and the complex preparation process, which dramatically inhibited their transportation and installation in areas with poor infrastructure. Therefore, there is an urgent need to develop a universal method to fabricate flexible solar evaporators. Herein, a novel solar evaporator that integrates a flexible matrix (Cu mesh or textile) and a hierarchical Fe-MOF-74 photothermal absorber component is perfectly prepared for the rapid and efficient SDISG. Notably, the results show that Fe-MOF-74-based flexible textile matrix composites exhibit outstanding light absorption (83.81%), low thermal conductivity (0.1730 W/m K), super hydrophilic properties (within 50 ms, the contact angle is close to 0°), excellent salt resistance, high evaporation rate (1.35 kg/m2 h), and photothermal conversion efficiency (η is 81.5% under one sun, stable for 30 days). Owing to the flexibility, recyclability, and above-mentioned excellent performance, the prepared hierarchical Fe-MOF-74-based flexible composite systems are more practical for transportation, large-scale production, and stable and efficient applications. As a result, this work offers new insight into the future development of the combination of a MOF-based photothermal absorber and flexible substrates, as well as for the application of interfacial solar seawater desalination, and provides a new reference for other applications.