Precise Design of D-A Type Metal Covalent Organic Framework for Regulating Intramolecular-Charge-Transfer toward HO Photosynthesis.

For most organic structures, the donor-acceptor (D-A) effect can effectively regulate the separation efficiency of photogenerated carriers, thereby enhancing the photocatalytic performance. However, the internal correlation between the structure and charge transportation, especially at the molecular level, is insufficiently explored. Herein, Cu(PyCA) (PyCA = pyrazolate-4-carboxaldehyde), tris(4-aminophenyl) amine, and [2,2'-bipyridine]-5,5'-diamine were employed to prepare two metal-covalent organic frameworks (MCOFs), namely, Tap-MCOF and Bpy-MCOF, both of which are D-A-type structure. In accordance, Tap-MCOF exhibits improved conversion of HO and O to HO in the absence of sacrificial agent, achieving the HO production rate of 288.58 μmol g h, which is approximately 2.7-fold higher than that of Bpy-MCOF. It is considered due to the intensified D-A effect within Tap-MCOF, it presents a narrower band gaps and greater separation of photoinduced carriers, compared with that of Bpy-MCOF. The transient photocurrent response intensity of Tap-MCOF is significantly higher than that of Bpy-MCOF, indicating its superior charge separation and transport efficiency. These results not only provide a strategy for manipulating the carrier separation efficiency of photocatalysts at the molecular level but also furnish insights into the effective photocatalytic ORR and WOR transformations of organic semiconducting catalysts.