Bridges engineering manipulated exciton dissociation and charge separation in small acceptors of PDI supramolecular for boosting photocatalytic nitrogen fixation

Constructing acceptor–donor units (D/A) of polymer is an efficient method for promoting carrier separation to optimize photoreactivity. However, the carriers across the D/A interface of micromolecule was relatively hindered by the Coulomb potential. In this work, the polarity-bridged acceptor–donor units of perylene-3,4,9,10-tetracarboxylic acid diimide (PDI) composite (BOPDI) has been constructed using a simple strategy. The improved BOPDI achieves excellent photocatalytic nitrogen fixation rate (74.0 μmol g−1h−1) as well as stability without using any co-catalyst and sacrificial agent, which is 11 times that of the original PDI group. DFT calculations and experimental results show that the polarity-bridges reasonably adjusts the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) bands and absorption characteristics, ensuring the BOPDI absorbed near-infrared light and activated N2 molecules. In addition, the polarity bridged units strengthen the construction of the built-in electric field for overcoming the Coulomb potential, resulting in a higher carrier separation and exciton dissociation efficiency. This work not only provides a tactics for enhancing the electronic transmission of D/A units, but also expanding the application research of PDI composite materials in the photocatalytic reduction of nitrogen.