Controlling Selectivity for Efficient Nitrogen Photo-Fixation Over Hydrogen Evolution using Anthracene-Containing D-A...

Donor-acceptor (D-A) structured organic photocatalysts have garnered considerable attention for artificial NH₃ photosynthesis under ambient conditions. Nevertheless, their N₂ photo-fixation efficiency is constrained by insufficient chemisorption and selectivity towards N₂. Herein, we rationally designed a series of conjugated polymers with varying donor-to-acceptor molar ratios using anthracene and dibenzothiophene sulfone (BTSO) as electron-donor and electron-acceptor units. The production rate of the nitrogen reduction reaction (NRR) increases progressively with higher anthracene content. Notably, AnSO-6, featuring a 1:1 donor-to-acceptor molar ratio, achieves a remarkable NH₃ production rate of 1645.25 µmol g^-1 h^-1 under full-spectrum irradiation without sacrificial agents. This enhancement stems from the superior N₂ chemisorption capability, high electron transfer activity, and efficient charge separation endowed by the unique D-A structure. By contrast, the photocatalytic hydrogen evolution reaction (HER) exhibits an inverse trend, indicating the feasibility of tuning HER/NRR selectivity via donor-to-acceptor ratio adjustment. Additionally, the generality of the BTSO-based D-A platform was validated by substituting anthracene with diverse electron donors, demonstrating broad applicability for efficient photocatalytic N₂ fixation. This research establishes a promising approach to boost photocatalytic NH₃ production and offers novel insights into modulating the equilibrium between NRR and HER through precise regulation of the donor-to-acceptor monomer ratio.