Sulfonate-Rich COF-Based\nCNT Composites for Efficient\nSolar-Driven Membrane Evaporators and Lithium–Sulfur Battery-Modified\nSeparators

Covalent organic frameworks (COFs) hold great promise\nin the realm\nof energy conversion and utilization, but their applications are hampered\nby their narrow-band spectral response, difficult framework design,\nand low conductivity at the moment. Here, we designed COF-based carbon\nnanotubes (CNTs) composites containing sulfonic groups (TB-COF@CNTs),\nwhich have good performance in seawater desalination and lithium–sulfur\n(Li–S) batteries. In seawater desalination, this TB-COF@CNTs\nmembrane evaporator possesses a 97% solar absorption efficiency (at\n300–2500 nm), low evaporation enthalpy (2020 kJ kg<sup>–1</sup>), and high rate of evaporation (1.72 kg m<sup>–2</sup> h<sup>–1</sup>) and high efficiency (96.5%) (at one sun irradiation).\nSignificantly, the SO<sub>3</sub><sup>–</sup> groups can effectively\nseparate anions (for instance, Cl<sup>–</sup>) from cations\n(for instance, Na<sup>+</sup>) in the evaporator, preventing the production\nof solid-salt crystals during the evaporation process. In Li–S\nbatteries, the TB-COF@CNTs-modified separator can also slow down the\nshuttle of polysulfide and facilitate the migration of lithium ions,\ndemonstrating exceptional electrochemical performance, as its initial\nspecific capacity was 833 mA h g<sup>–1</sup> at 0.5 C and\nsubsequently demonstrated 633 mA h g<sup>–1</sup> after 200\ncycles. Our study presents a feasible approach to rationally design\nfunctional COFs-based CNT composites, thereby enhancing their potential\napplications in integrated energy systems.