Kagome-topology 2D covalent organic frameworks assembled from D_2h-symmetric and non-centrosymmetric C₂-symmetric blocks for photothermal imaging

In this study, we synthesized two new two-dimensional (2D) covalent organic frameworks (COFs), COF-TA and COF-DP, by combining 4-connected D-2h-symmetric and 2-connected non-centrosymmetric C-2-symmetric building blocks. Unlike the typical sql topology, these COFs exhibit an unconventional kgm topology characterized by a favorable anti-parallel stacking arrangement, which results in a lower energy configuration. Notably, COF-DP, with its unique D-A-D structural motif and photosensitive properties, demonstrates a narrow band gap and excellent photothermal conversion capabilities, making it a promising material for photothermal imaging applications.