Enhancing Near-Infrared Absorption by Modulation the Intermediate Band of Cu–Fe–S Semiconductors for Boosting Photocatalytic Hydrogenation of Nitroarenes

The trade-off between maximizing light harvesting efficiency and maintaining high photoredox potentials is still a persistent and fundamental challenge in the field of photocatalysis. Intermediate band semiconductors (IBSCs) offer a promising approach to address the challenge by introducing an additional energy level within the bandgap, enabling simultaneous absorption of low- and high-energy photons while preserving strong redox capabilities. Herein, three kinds of Cu–Fe–S IBSC nanocrystals, i.e., Cu5FeS4 nanodisks (NDs), CuFeS2 NDs, and CuFeS2 octahedrons (Octas), have been controllably synthesized and they exhibit full spectral absorption capability, especially in the near-infrared (NIR) region extending to a wavelength of over 2500 nm. Notably, the Fe content-dependent NIR absorption enhancement has been revealed, originating from the modulation of the IB position within the band, as confirmed by theoretical calculation. These IBSCs can achieve NIR and full-spectrum photocatalytic transformation of 3-nitrostyrene to 3-vinylaniline with excellent conversion and selectivity and also possess broad applicability for various nitrobenzene derivatives. Under full-spectrum irradiation, CuFeS2 Octas exhibit a turnover frequency of up to 13.0 h–1, surpassing most reported nonprecious metal-based photo- and thermocatalysts. This study provides insights into the design of the IBSCs with optimal absorption capability and photoredox potentials, further enhancing the performance of the IBSC-based photocatalysts.