Mimicking the photosynthetic system in nature and developing photocatalytic technology to transform solar light into usable synthetic energy is a practical approach to address the energy crisis and environmental contamination issues.In this domain,photocatalysts are the central components of photoabsorption and electron transfer,critical factors determining photocatalytic efficiency.Thus,developing high-efficiency photocatalysts is a fundamental scientific and technological challenge for efficient photosynthesis.Nevertheless,the photosensitizers applied in conventional catalytic schemes generally suffer from weak absorption capacity of visible light,the short lifetime of triplet excited states,inadequate oxidation-reduction capacity,poor photocatalytic stability,and non-recyclability,which are unfavorable to the exploitation of high-efficiency photosynthetic systems.To solve the issues described above,this article constructs the coupling between coumarin organo-small molecule chromophores and metal-ligand centers to enhance the photosensitizing ability of metal coordination,self-assembled and synthesized pyrene-like organic small molecules to enhance the recycling performance of photosensitizers.The detailed work was performed as follows:They first constructed a series of composite photosensitizers(Ru-2 and Ru-3)possessing visible absorption in solids and long-excited state longevity by covalently coupling coumarin minor molecules with ruthenium ligand centers.In particular,the band containing three coumarin small molecules,Ru-3,has well visible light absorbance with a molar absorption coefficient of 144000 M-1 cm-1,which is 13 times higher than that of the conventional Ru(bpy)3(PF6)2(Ru-1)photosensitizer.In addition,the excited state lifetime of Ru-3 is as long as 14.7μs,which is 18 times higher than that of the conventional Ru-1 complex.Under visible light irradiation,Ru-3 can efficiently produce hydrogen by hydrogen decomposition with a hydrogen production TON of 5510,and under low power irradiation,Ru-3 is 27 times more active than conventional Ru-1.The systematic study shows that the small molecule-sensitized ruthenium coordination center can realize the separation of the light absorption center and redox center,which can significantly improve the light capture ability and excited state lifetime of the system,the light energy utilization and inter-component electron transfer efficiencies in turn.In addition,the self-assembly of tetra carboxy pyrene-like small molecules was performed under mild conditions to achieve an ordered heterogeneous phase of the molecular photosensitizer,and the nano-HOF photosensitizer was constructed.Pt@nano-HOF is a new compound photocatalyst that can effectively drive hydrogen generation by photodissociation with a hydrogen production rate of 31.2 mmol g-1 h-1,more than 23 times higher than that of nano-HOF.Moreover,the composite demonstrated superior photochemical stabilization.It can be recirculated more than five times and still maintain high catalytic activity,and the structure and crystallinity of the photocatalyst remain unchanged.This systematic research indicates that the direct coupling of platinum nanoparticles with HOF heterogeneous photosensitizers accelerates the transfer of hot electrons from the nano-HOF to the platinum catalyst and enhances the photochemical sustainability and photolytic hydrogen performance of HOF.This study provides the essential scientific reference for developing efficient,stable,and recyclable heterogeneous photocatalysts for efficient hydrogen production from photolyzed water.In conclusion,a CO2-limited coupling strategy was developed to eliminate the limitations of the precious metal Pt-containing composite catalysts mentioned above to accelerate the rapid transfer of photogenerated electrons from the HOF photosensitizer to CO2,thus enhancing the photolytic hydrogen production performance.The hydrogen production of the nano-HOF photosensitizer in the CO2atmosphere is up to 188.4μmol,which is six times higher than that in the argon atmosphere.Through photoelectrochemical characterization techniques and DFT theoretical calculations,these HOF photosensitizers have the advantages of moderate surface spacing and strong interfacialπ-πsupramolecular interactions,which help interlayer domains to confine CO2 molecules,thus improving the hydrophilicity and electron-hole separation efficiency of HOF,and finally achieving efficient hydrogen production by hydrolysis.This research work provides a new concept for developing metal-free high-efficiency photocatalysts. |