Functional Group-Mediated Evaporation Enthalpy and Nanoconfinement-Engineered Water Clusters’ Synergy in Versatile MXene/iCOFs Hydrogels for Salt-Resistant Solar-Driven Interfacial Evaporation

Solar-driven interfacial evaporation (SDIE) has emerged as a promising solution for sustainable brine management and water purification. However, traditional SDIE systems face a trade-off between evaporation performance and salt resistance. Herein, we demonstrate that a novel functional group-mediated and nanoconfinement-engineered hydrogel composed of MXene and ionic covalent organic frameworks (iCOFs) effectively regulates both evaporation performance and salt resistance. The iCOFs with a high density of hydrophilic functional groups and nanoconfinement effect are found to simultaneously induce the disruption of hydrogen bonding networks and enhance cluster evaporation, achieving reduced evaporation enthalpy. The increased functional groups also facilitate both ion reverse diffusion and the Donnan effect, which effectively alleviates salt crystallization during long-term seawater desalination. This strategy leads to a 56% enhancement in evaporation rate (2.91 kg m^-2 h^-1 under 1 sun) of the optimized hydrogel. The evaporation performance remains stable in highly concentrated (20 wt %) saline and also during a 60 h continuous operation in seawater. In addition, functional group-mediated MXene/iCOFs hydrogels with a nanoconfinement effect exhibit a 99.99% removal rate for various water pollutants, including heavy metal ions, antibiotics, and dyes, while maintaining stable performance under extreme temperature conditions. This study offers a new strategy for designing programmable SDIE for future sustainable water treatment technology.