Two-Dimensional Metal Covalent Organic Polymers with Dirhodium(II) Photoreduction Centers for Efficient Nitrogen Fixation

Photocatalytic nitrogen fixation is a green method for converting N₂ to NH₃, but it remains a challenging task due to the lack of effective photocatalysts. Herein, a series of porous metal covalent organic polymers (MCOPs) with the integration of dinuclear rhodium(II) catalytic centers were rationally constructed for photocatalytic N₂ fixation. Interestingly, the porous MCOPs had double-layers two-dimensional (2D) structures with the coordinated Rh(II) as the point of registry. The photocatalytic experiment showed that Rh-TAPA with significant donor-acceptor (D−A) features exhibited a high activity toward NH₃ production with a rate of 319.8 μmol g⁻¹ h⁻¹. The electron transfer process, N₂ adsorption and activation mechanism of RhCOPs were further investigated through comprehensive characterization, including DFT calculations and in situ characterization. This work provided a valuable insight into the photocatalytic N₂ fixation process with porous materials.