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The high local electron density and efficient charge carrier separation are two important factors to affect photocatalytic activity, especially for the CO2 photoreduction reaction. However, the systematic studies on the structure‐functional relationship regarding the above two factors based on precisely structure model are rarely reported. Herein, as a proof‐of‐concept, we developed a new strategy on the evaluation of local electron density by controlling the relative electron‐deficient (ED) and electron‐rich (ER) intensity of monomer at a molecular level based on three rational‐designed vinylene‐linked sp2 carbon‐covalent organic frameworks (COFs). As expected, the as‐prepared vinylene‐linked sp2 carbon‐conjugated metal‐covalent organic framework (MCOFs) (VL‐MCOF‐1) with molecular junction exhibited excellent activities for CO2‐to‐HCOOH conversion (283.41 μmol g−1 h−1) and high selectivity of 97.1 %, much higher than the VL‐MCOF‐2 and g‐C34N6‐COF, which is due to the synergistic effect of the multi‐electronic metal clusters (Cu3(PyCA)3) (PyCA=pyrazolate‐4‐carboxaldehyde) as strong ER roles and cyanopyridine units as ED roles and active sites, as well as the boosted photo‐induced charge separation efficiency of vinyl connection and increased light utilization ability. These results not only provide a strategy for regulating the electron‐density distribution of photocatalysts at the molecular level but also offers profound insights for metal clusters‐based COFs to effective CO2 conversion. [ABSTRACT FROM AUTHOR]

In this work, we innovatively assembled two types of traditional photosensitizers, that is pyridine ruthenium/ferrum (Ru(bpy)32+/Fe(bpy)32+) and porphyrin/metalloporphyrin complex (2HPor/ZnPor) by covalent linkage to get a series of dual photosensitizer‐based three‐dimensional metal‐covalent organic frameworks (3D MCOFs), which behaved strong visible light‐absorbing ability, efficient electron transfer and suitable band gap for highly efficient photocatalytic hydrogen (H2) evolution. Rubpy‐ZnPor COF achieved the highest H2 yield (30 338 μmol g−1 h−1) with apparent quantum efficiency (AQE) of 9.68 %@420 nm, which showed one of the best performances among all reported COF based photocatalysts. Furthermore, the in situ produced H2 was successfully tandem used in the alkyne hydrogenation with ≈99.9 % conversion efficiency. Theoretical calculations reveal that both the two photosensitizer units in MCOFs can be photoexcited and thus contribute optimal photocatalytic activity. This work develops a general strategy and shows the great potential of using multiple photosensitive materials in the field of photocatalysis. [ABSTRACT FROM AUTHOR]