Highly selective synthesis of interlocked carbazole-based cages and their applications in photothermal seawater desalination

The design and assembly of interlocked supramolecular cages is of interest due to their exquisite topological configuration and excellent performance in a variety of applications. We introduce two carbazole-based ligands L1 and L2, they combine with four distinct half-sandwich rhodium building blocks to form three molecular-tweezer-like compounds, three interlocked cages, tetranuclear macrocycle, and hexanuclear cage. Stacking interactions between carbazole groups facilitate the formation of interlocked structures. Single-crystal X-ray diffraction, Nuclear Magnetic Resonance Spectroscopy and Electrospray Ionization Mass Spectrometry determine their structures. The compounds 5(OTf)₁₂, 6(OTf)₁₂ and 7(OTf)₁₂ exhibit broad-band absorption from Ultraviolet-Visible Spectroscopy to the Near-Infrared regions and remarkable photothermal conversion. They are incorporated into membranes 5'(OTf)₁₂, 6'(OTf)₁₂, and 7'(OTf)₁₂, whose applications in solar energy-driven steam generation are studied. Evaporation rates of 0.77, 1.52, and 1.37 kg·m^-2·h^-1 are recorded for 5'(OTf)₁₂, 6'(OTf)₁₂, and 7'(OTf)₁₂, respectively, indicating their suitability to collect fresh water from desalination and wastewater treatment.