Size Modulation of Covalent Organic Frameworks for Enhanced Solar-Driven Photothermal Evaporation Efficiency

Solar-driven interfacial water evaporation has emerged as a promising sustainable approach to address global water scarcity challenges. Herein, the development of a series of diketopyrrolopyrrole (DPP)-embedded covalent organic framework (COF) nanospheres via a mild ultrasound-assisted synthetic protocol, strategically engineered as high-performance photothermal materials is reported. A systematic investigation into size modulation effects on interfacial photothermal performance is conducted by flexibly adjusting the size of COF nanospheres. Nanoscale engineering of COF spheres revealed that reduced particle sizes can enhance light absorption, synergistically reduce water evaporation enthalpy, and optimize intermediate water (IW) content. Therefore, the DPPT-1 COF films demonstrate an encouraging photothermal performance, achieving a remarkable water evaporation rate of 3.45 kg m^-2 h^-1 under one sun irradiation, with a solar-to-vapor efficiency of 95.09%. Notably, the DPPT-1 system demonstrates exceptional environmental adaptability, enabling efficient production of potable water from strongly acidic, alkaline, and natural seawater matrices. This research elucidated the pivotal role of size modulation in modulating photothermal evaporation kinetics of COF nanosphere, thus providing design principles for tailored nanoscale engineering of COFs toward sustainable water purification technologies.