Two-dimensional p-π conjugated amide-linked polymeric photocatalysts with enhanced carrier separation

Two-dimensional (2D) polymers have recently emerged as a hot topic in photocatalysis because of their rich active sites, tunable topology, and electronic structures. However, they typically suffer from severe photogenerated charge recombination, which hinders further elevation in photocatalytic performance. Here, we develop a method of direct condensation between amino and carboxyl groups to prepare a series of 2D polyaramids (2DPAs). Compared with the conventional fully π-conjugated 2D polyimide (2DPI), one of the 2DPAs (denoted as 2DPA-PPA) has an almost identical molecular skeleton but features a close yet spatially separated HOMO and LUMO distribution (the recombination rate is below 1/3 that for 2DPI, and the charge separation state lifetime is 5.5 times as long). Consequently, the rate of photocatalytic O₂ activation over 2DPA-PPA is at least 5 times higher than that over 2DPI. Our findings on the preparation of 2DPAs and catalytic mechanism would be of guidance for designing high-performance photocatalysts.