Fully Conjugated Covalent Porous Polymers for Highly Efficient Solar-Thermal Conversion

Solar-thermal water evaporation is a promising strategy for the clean water production. Developing photothermal conversion materials with high efficiency and stability is both urgent and challenging. Herein, we report two fully conjugated bipyranylidene-based microporous polymers (DP-CMP1 and DP-CMP2) for the first time, that feature broad light absorption, superior photothermal efficiency, and outstanding durability. Under the illumination of 660 nm laser with 100 mW cm^-2, the temperature of DP-CMP1 drastically increased from 29.1 to 174.7 °C within 4 s. Furthermore, an interfacial heating evaporation system based on DP-CMP1 achieved high solar thermal water evaporation rates of 3.83 and 3.77 kg m^-2 h^-1 under 1 sun illumination for pure water and seawater, with excellent energy conversion efficiency of 97.5 and 96.6%, respectively. Multiple spectroscopic and theoretical investigations reveal DP-CMP1 is intrinsically an outstanding photothermal material owing to its small band gap, fast nonradiative combination rate, large nonadiabatic coupling value, and stronger electron-phonon coupling.