Synthesis And Photocatalytic Performances Of Novel Bodipy Photosensitizers

Photocatalytic technology is a promising way to solve energy and environmental problems by converting solar energy into chemical energy.The photosensitizer is a key component of the photocatalytic system that absorbs light and transfers electrons and energy,influencing the photosynthesis efficiency.However,most photosensitizers have drawbacks such as noble metal content and modification difficulty,which limit the performance of photosynthesis systems.Boron dipyrromethene（Bodipy）photosensitizers are attractive candidates for artificial photosensitizers due to their high molar extinction coefficient,strong modifiability and high stability.However,Bodipy relies on heavy atoms（I,Br,etc.）to enhance the intersystem crossing（ISC）efficiency.The use of Bodipy without heavy atoms in photocatalysis research is rare,and its structure-activity relationship is poorly understood.Furthermore,most photosensitizers in photocatalysis field mainly absorb ultraviolet light,and there is a lack of photosensitizers that can be excited by red or near-infrared light.Developing Bodipy photosensitizers that respond to deep red or near-infrared light poses a significant challenge.In this study,we designed and synthesized pure organic photosensitizers with different absorption ranges by extending the conjugate structure of Bodipy motif,and evaluated their photocatalytic properties.The main research contents are as follows:Firstly,we designed a series of organic photosensitizers（B-1─B-6）based on Bodipy and anthracene units for hydrogen production by visible-light-driven water splitting.These photosensitizers have orthogonal donor-acceptor structures that facilitate intersystem crossing（ISC）and long-lived triplet excited states.By introducing different aromatic aldehydes to Bodipy,we tuned their absorption spectra to cover more than 80%of the visible light region.Among them,B-3 showed the best performance in sensitizing a nickel catalyst for hydrogen evolution under visible light irradiation atλ>600 nm,surpassing the benchmark Ru（bpy）₃²⁺.We attribute this to its strong red light absorption,long triplet lifetime and high photostability.Our work demonstrates the potential of pure organic photosensitizers with long-wavelength excitation for efficient and sustainable catalytic systems.Photocatalytic water splitting for hydrogen production is a promising strategy for clean energy generation.However,most photosensitizers（PSs）for this process have limited light absorption in the visible range.Here,we report a series of organic PSs（NIB-1─NIB-3）with deep red to near-infrared light absorption and high photostability.Among them,NIB-1 exhibited the best performance for hydrogen evolution,with a turnover number（TON）of 305 under visible light（λ>420 nm）and 147 under deep red light（λ>600 nm）,which were significantly higher than those of NIB-2 and NIB-3.The superior activity of NIB-1 was attributed to its efficient intramolecular and intermolecular electron transfer processes,as revealed by systematic studies.Our work demonstrates the potential of designing red-light-excited organic PSs for photocatalytic water splitting and provides insights into the structure-activity relationship of these PSs.Finally,to match the broadband luminescence characteristics of the solar spectrum,this chapter constructs wide-spectrum absorption organic photosensitizers（BOD-1─BOD-4）based on Bodipy units with intramolecular energy transfer effects.Among them,BOD-2 and BOD-4 both exhibit dual light absorption channels in the visible region,significantly improving the utilization of sunlight.Under visible light irradiation,BOD-2 can efficiently oxidize DHN to produce the drug molecule juglone,with a conversion rate of 97.3%within 25 minutes,higher than the B-4 and noble metal Ru and Ir-based complexes.Among them,the initial reaction rate driven by BOD-2 was 6.2×10^-2 min^-1,nearly twice as fast as BOD-1,and it was 31-fold and7.6-fold higher than traditional noble metal photosensitizers[Ru（bpy）₃]²⁺and[Ir（ppy）₃]⁺,respectively.Systematic studies show that the new multi-component organic photosensitizers have strong and wide visible light absorption capabilities,long excited state lifetimes and excellent photocatalytic stability,which help to improve the utilization of light energy and intermolecular energy transfer efficiency,and thus improve photosynthesis efficiency.This work combines Through-Bond Energy Transfer（TBET）and Spin-Orbit Charge Transfer Intersystem Crossing（SOCT-ISC）strategies to construct wide-spectrum and long-excited state lifetime Bodipy photosensitizers,providing new ideas for developing highly efficient wide-spectrum absorption photosensitizers.