Marriage of 2D Covalent–Organic Framework and 3D Network as Stable Solar-Thermal Still for Efficient Solar Steam Generation

In this work, a diketopyrrolopyrrole-based 2D covalent–organic framework (COF) is realized and featured with broadband optical absorption and high solar-thermal conversion performance. Moreover, a 3D hierarchical structure, referred to as COF-based hierarchical structure (COFHS), is rationally designed to achieve an enhanced photothermal conversion efficiency. In this water evaporator, diketopyrrolopyrrole is immobilized into conjugated COF to achieve enhanced light absorption, whereas a porous PVA network scaffold is utilized to support COF sheets as well as to enhance the hydrophilicity of the evaporator. Due to this structural advantage, COFHS displays a high solar-to-vapor energy conversion efficiency of 93.2%. Under 1 sun AM1.5 G irradiation, a stable water evaporation rate of 2.5 kg m^–2 h^–1 can be achieved. As a proof-of-concept application, a water collection device prepared with the COFHS can achieve high solar-thermal water collection efficiency of 10.2 L m^–2 d^–1 under natural solar irradiation. The good solar-thermal conversion properties and high-water evaporation rate make the COFHS a promising platform for solar-thermal water production.