Beyond Tradition: A MOF-On-MOF Cascade Z-Scheme Heterostructure for Augmented CO Photoreduction.

Metal-organic frameworks (MOFs) are rigorously investigated as promising candidates for CO capture and conversion. MOF-on-MOF heterostructures integrate bolstered charger carrier separation with the intrinsic advantages of MOF components, exhibiting immense potential to substantially escalate the efficiency of photocatalytic CO reduction (CORR). However, the structural and compositional complexity poses significant challenges to the controllable development of these heterostructures. Herein, a conventional MOF-on-MOF nanocomposite is readily optimized from a type II heterojunction to a state-of-the-art cascade Z-scheme configuration via the encapsulation of Pt nanoparticles (Pt NPs), establishing synergistic MOF-MOF and metal-MOF heterojunctions with reinforced built-in electric field. A cascade electron flow is thus propelled, vigorously separating the photogenerated charge carriers and profoundly extending their lifetimes. Collectively, the photocatalytic activity of the cascade Z-scheme is drastically promoted, exhibiting a nearly quintuple enhancement in the CO production rate over the original type II heterostructure. Moreover, the anti-sintering capacity of the developed nanocomposite is unveiled, elucidating its simultaneously improved activity and stability. These findings present unprecedented regulation over the configuration of a MOF-on-MOF heterojunction, substantially enriching the fundamental understanding and rational design strategies of composite materials.