Highly Selective Synthesis of Interlocked Carbazole-based Cages and their Application in Effective Solar-driven Water Evaporation

The design and assembly of interlocked supramolecular cages is a highly important research topic, mainly due to their exquisite topological configuration and excellent performance in a variety of application fields. Herein, we introduce the preparation of two new carbazole-based ligand precursors, L1 and L2, which were rationally designed to form three molecular-tweezer like compounds, three interlocked cages, a tetranuclear macrocycle and a hexanuclear cage via combination with four different half-sandwich rhodium based building blocks, E1-E4. The structure of these compounds was determined by single crystal X-ray diffraction analysis, NMR spectroscopy and ESI-TOF-MS analysis. Owing to stacking interactions between carbazole groups and the appropriate size of building blocks, interlocked cages and molecular-tweezer like compounds were obtained. Furthermore, the photothermal conversion performance of the isolated compounds was studied in detail. The interlocked cages 5, 6, and 7, exhibiting broad-band absorptions from the UV-Vis to the NIR region and remarkable photothermal conversion, were used to prepare the membranes 5', 6', and 7', and study their application in steam generation promoted by solar energy. Evaporation rates of 0.77, 1.52 and 1.37 kg·m-2·h-1 were recorded for 5', 6' and 7', respectively, indicating their suitability to collect fresh water from desalination and wastewater treatment.