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

Abstract

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. 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. Here, the authors synthesize interlocked cages from half-sandwich rhodium building blocks and prepare membranes for applications in photothermal seawater desalination.