Chemical Modification of Platinum-Based Photothermal Polymer toward Enhanced Solar Absorption and Steam Generation

Photothermal materials possessing broad-spectrum light absorption is crucial for improving the efficiency of interfacial solar steam generation system. Organometallic polymers exhibit great potential as photothermal materials because their light absorption capabilities can be enhanced through strategic molecular design. Herein, two new polymers, designated M1 and M2, are designed and synthesized via the polymerization of platinum complexes and an organic acceptor group. Their photothermal performance is evaluated by fabricating solar evaporators through depositing M1 or M2 onto porous polyurethane foam. Compared to M2, the M1-based evaporator achieves a water evaporation rate of 1.87 kg m^-2 h^-1 (33.57% higher) under 1 sun, due to its enhanced light-absorbing capability in the UV-vis-NIR region. This evaporator excels in desalinating natural seawater, highly concentrated brine (maximum 20 wt.% NaCl), and purifying dye-contaminated water. Its excellent salt rejection capability through the salt-ion diffusion mechanism showcases its suitability for prolonged operational use. The outdoor desalination system, featuring the evaporator, demonstrates the potential to generate approximately 8.5 L m^-2 of freshwater in 8 h under an average solar irradiance of 0.58 kW m^-2. This research highlights the effective molecular design in organometallic photothermal polymers for enhanced solar steam generation and demonstrates their potential in solar desalination applications.