Integrating Tetrathiafulvalene and Nickel-Bis(dithiolene) Units into Donor-Acceptor Covalent Organic Frameworks for Stable and Efficient Photothermal Conversion

Tetrathiafulvalene (TTF) and Ni-bis(dithiolene) are typical conductive units widely studied in electronics, optics, and photochemistry. However, their applications in near-infrared (NIR) photothermal conversion are often limited by insufficient NIR absorption and low chemical/thermal stability. Herein, we integrate TTF and Ni-bis(dithiolene) into a covalent organic framework (COF) with stable and efficient NIR and solar photothermal conversion performance. Two isostructural COFs, namely Ni-TTF and TTF-TTF, are successfully isolated which are composed of TTF and Ni-bis(dithiolene) units as donor-acceptor (D-A) pairs or TTF units only. Both COFs show high BET surface areas and good chemical/thermal stability. Notably, compared with TTF-TTF, the periodic D-A arrangement in Ni-TTF significantly lowers the bandgap, leading to unprecedented NIR and solar photothermal conversion performance.

Redox-Active Mixed-Linker Metal-Organic Frameworks with Switchable Semiconductive Characteristics for Tailorable Chemiresistive Sensing

Metal-organic frameworks (MOFs), with diverse metal nodes and designable organic linkers, offer unique opportunities for the rational engineering of semiconducting properties. In this work, we report a mixed-linker conductive MOF system with both tetrathiafulvalene and Ni-bis(dithiolene) moieties, which allows the fine-tuning of electronic structures and semiconductive characteristics. By continuously increasing the molar ratio between tetrathiafulvalene and Ni-bis(dithiolene), the switching of the semiconducting behaviors from n-type to p-type was observed along with an increase in electrical conductivity by 3 orders of magnitude (from 2.88×10^-7  S m^-1 to 9.26×10^-5  S m^-1 ). Furthermore, mixed-linker MOFs were applied for the chemiresistive detection of volatile organic compounds (VOCs), where the sensing performance was modulated by the corresponding linker ratios, showing synergistic and nonlinear modulation effects.