Covalent organic frameworks with ultra-broadband absorption for efficient solar-driven water evaporation

Covalent organic frameworks (COFs) demonstrate application prospects in solar-driven water evaporation (SDWE). Nevertheless, the reported COFs intrinsically lack the capacity to harvest infrared light, which results in inferior photothermal conversion efficiency and thereby retards the water evaporation rate. Here we report a class of Cl-functionalized COFs with ultra-broadband absorption spanning 200–1,500 nm and strong non-radiative relaxation capacity for enhancing SDWE performance. The synthesized TTB-pPA COFs (where TTB is 2,4,6-trichloro-1,3,5-trialdehyde benzene and pPA is p-phenylenediamine) exhibit a notable temperature rise to 125.3 °C within 60 s under 1-sun illumination, superior to that of COFs without Cl atom (60.7 °C). The SDWE device was constructed by using TTB-pPA COFs as photothermal conversion layer, showing an elevated water evaporation rate of 7.62 kg m⁻² h⁻¹, which significantly outperform previously reported water evaporation device. Furthermore, the custom-developed water evaporation device demonstrates long-term stability of 60 days under natural light conditions, together with the pure water production (impurity content <0.1%) of 30–45 l m⁻² d⁻¹, which can meet the drinking water needs of 12–18 people. Overall, this work emphasizes the significance of designing COFs with a broad light absorption range and strong non-radiative electron decay capability in enhancing solar-powered seawater desalination capability.