Engineering S-Scheme Heterojunction via MOF-on-MOF for Photocatalytic Nitroarene Hydrogenation

Photocatalytic nitroarene reduction provides a promising strategy for the sustainable production of aniline. The construction of S-scheme heterostructures with a clear interfacial charge transfer mechanism is considered as an effective strategy to improve the photocatalytic performance of photocatalysts. The assembly of MOF-on-MOF might be used to construct S-scheme heterojunctions due to the rich structures, effective charge transport channels, and fast mass transfer of MOFs. Herein, 2D Pd-PPF-1 was coated on 3D Pd-PCN-222 through a presurface modification strategy, and the prepared Pd-PPF-1/Pd-PCN-222 with an S-scheme heterojunction displayed the morphology of a 2D nanoflower winding around a 3D rod. As for photocatalytic nitroarene hydrogenation, the as-obtained Pd-PPF-1/Pd-PCN-222 catalyst exhibited much higher photocatalytic performance than Pd-PPF-1, Pd-PCN-222, or a physical mixture of Pd-PPF-1 and Pd-PCN-222. The high catalytic performance of Pd-PPF-1/Pd-PCN-222 might be attributed to the formation of the S-scheme heterojunction, which not only retained the redox capability of the parent MOFs but also separated photogenerated carriers. This work presents a constructive route for designing 2D-on-3D MOF S-scheme heterojunction with controllable morphology and high photocatalytic ability.