Azulene-based conjugated microporous polymer integrated with hydrophobic vertical-channel aerogel for enhanced photothermal desalination

Abstract

Conjugated microporous polymers (CMPs) possess tunable conjugated backbones and band structures, which promote broadband light absorption and non-radiative transition of photogenerated charge carriers, thereby endowing them with excellent photothermal conversion capability. However, conventional photothermal evaporation materials suffer from limited light absorption range and salt crystallization blockage, restricting the improvement of evaporation efficiency. In this work, we designed and synthesized a novel azulene-based conjugated microporous polymer (CMP-A) with moderate accessible porosity. Its asymmetric π-conjugated structure endows it with a broadband absorption of ∼92% in the range of 200–1400 nm and excellent photothermal conversion capability. Furthermore, we constructed the CMP-A@PVDF evaporator by loading CMP-A onto the top of a hydrophobic poly (vinylidene fluoride) (PVDF) aerogel with vertically aligned channels. The evaporator utilizes the hydrophobic vertical channels for rapid water transport and salt rejection, while enabling efficient photothermal evaporation via CMP-A. Under 1 sun irradiation, the CMP-A@PVDF evaporator achieves a high evaporation rate of 2.16 kg m−2 h−1 (5.14 times that of pure water) and a photothermal conversion efficiency as high as 98.2%. No salt accumulation is observed after 30 cycles, demonstrating excellent desalination performance and salt-resistant stability. This work provides a new design strategy for constructing high-performance photothermal materials.