Two-dimensional covalent organic frameworks with spatial-distribution defined D-A structures for efficient near-infrared photothermal conversion

Two naphthalene diimide (NDI) based covalent organic frameworks (COFs) with stable diimide linkages were prepared by a condensation reaction between amine and anhydride. The spatially alternating distribution of electron-deficient NDI and electron-rich triphenylamine or 1,3,5-triphenylbenzene within the two-dimensional plane induces a charge transfer (CT) process resulting in significant near-infrared absorption characteristics. The different electron-donating behaviors led to a change in the photophysical properties and photothermal conversion properties. In addition, the photothermal conversion efficiency of NDI-N-COF with triphenylamine as a donor group reached 77.9%.