Persistent Radical Tetrathiafulvalene‐Based 2D Metal‐Organic Frameworks and Their Application in Efficient Photothermal Conversion

A series of stable radical 2D metal‐organic frameworks has been assembled. (m‐TTFTB)3 (m‐Tetrathiafulvalene‐tetrabenzoate) trimer building blocks are beneficial for the stability of the radicals due to delocalization of the unpaired electron. Hexanuclear rare‐earth‐cluster‐based 1D chains further enhance the stability of the frameworks. The radical state of the middle TTF in the trimer has been observed by the change of central C−C and C−S bond distances and the configuration of the TTF by single‐crystal X‐ray diffraction. The radical characteristics are also confirmed by electron paramagnetic resonance, UV/Vis–NIR absorption, and X‐ray photoelectron spectroscopy experiments. Stability tests showed that the radicals are stable even in solutions and under acid/base environments (pH 1–12). Owing to efficient light absorption due to intramolecular charge transfer, low thermal conductivity, and outstanding stability, the radical 2D Dy‐MOF shows excellent photothermal properties, an increase of 34.7 °C within 240 s under one‐sun illumination. The incorporation of TTF radical trimers and RE6 cluster SBUs result in a stable 2D radical MOF that is stable under harsh conditions including aqueous acid/base solutions. Exhibiting the characteristics of light absorption and excellent stability, the radical Dy‐MOF shows excellent photothermal conversion with an increase in temperature of 34.7 °C upon irradiation by one unit of sunlight within 240 s.