Thiazolo[5,4-d]Thiazole-Linked Conjugated Porous Organic Polymers for Visible Light-Driven C-N Bond Formation Reactions

Due to their unique semiconducting properties, conjugated porous organic polymers (CPOPs) have garnered significant interest in various photocatalysis applications. In this study, we synthesize three thiazolo[5,4-d]thiazole (TzTz)-linked CPOPs with three polyaryl rigid cores of benzene (CPOP1), pyrene (CPOP2), and triazine (CPOP3). We investigated their efficacy in catalyzing visible light-driven C-N bond formation reactions, including C-N cross-couplings between aryl bromides and amines and amination reactions from aryl bromides and sodium azides. Among the three, only CPOP2, combined with NiCl2 or Ni(dtbbpy)Cl2, effectively facilitated these transformations. Notably, CPOP2 exhibited photocatalytic activities approximately six times higher than its small molecular counterpart C1 in both reactions. The CPOP catalyst was easily recovered through centrifugal separation and reused for five catalytic cycles with minimal loss of activity. Theoretical calculations revealed that the deliberate structural design of polyaryl moieties could effectively tune the energy gap, which is crucial for the photocatalytic activity in organic reactions. This study, therefore, demonstrates a novel application of TzTz-linked CPOPs for heterogeneous photocatalytic organic transformations.