Novel ultrathin Bi@Fe-based metal-organic frameworks nanosheets for efficient solar-driven photocatalytic water purification: Synergistic effect of localized surface plasmon resonance and high-density exposed metal active centers.

Fe-based metal-organic frameworks (Fe-MOFs) have been extensively studied as fascinating photocatalysts due to their tunable structure and appealing light response. However, the application of traditional three-dimensional (3D) Fe-MOFs is limited by rapid carrier recombination and inaccessible active sites. In this work, a novel two-dimensional (2D) Bi decorated Fe-MOFs nanosheet photocatalyst was constructed, which exhibits significantly enhanced solar-driven photocatalytic activity due to the synergistic effect of localized surface plasmon resonance (LSPR) and surface high-density exposed metal active sites. Unlike 3D structures, 2D nanosheets enable surface densely exposed Fe-O clusters, which can be conveniently triggered by incident light to improve light response. 2D Fe-MOFs exhibit narrower bandgap and faster electron transfer thanks to the superior electronic effects of ultrathin nanosheets, including quantum confinement, electron delocalization and induction effects. Moreover, the unique 2D structure drastically reduces mass transfer resistance and guarantees quick pollutant diffusion, thus achieving adequate contact between pollutants and more accessible reactive sites. Bi nanoparticles (NPs), a non-precious plasma metal, further facilitate carrier separation and migration through LSPR effect. Driven by local electromagnetic field, photoinduced hot electrons move from Bi NPs to 2D Fe-MOFs, where they contribute to the production of active species. Meanwhile, light scattering effect of Bi NPs endows the catalyst with boosted light absorption by prolonging the incident photons path. With carbamazepine as target pollutant, the photocatalysis rate of 2D Bi decorated Fe-MOFs (Bi@Fe-MOFs) under solar light is 10.3 times that of 3D Fe-MOFs. This work provides new insights for designing MOFs photocatalysts with efficient solar-driven photocatalytic water purification.