Photocatalytic Property Of Porphyrin-Based Covalent Organic Framework For Environmental Analysis And Antibacterial Research

Porphyrin is a highly conjugatedπ-electron macrocyclic compound with excellent photophysical and redox properties,which can effectively activate the generation of reactive oxygen species（ROS）under the illumination of a certain light source.Meanwhile,porphyrins have been widely used as basic units of photosensitive porous materials such as metal organic frameworks（MOFs）,hydrogen-bonded organic frameworks（HOFs）,covalent organic polymers（COPs）,and covalent organic frameworks（COFs）.However,MOFs linked by coordination bonds and HOFs linked by hydrogen bonds are extremely unstable under extreme conditions such as strong acids,strong bases,and strong radioactivity due to their weak interactions.Amorphous COPs also hinder the exposure of catalytic sites and rapid mass transfer due to their poor crystallinity and irregular porosity.These constraints will bring challenges to practical applications.As a new class of crystalline porous materials,COFs have the advantages of large specific surface area,ordered and regular pore size,high stability,etc.,which can effectively overcome the shortcomings of the above materials and have a wide range of applications in catalysis,environmental monitoring,etc.In addition,metal-free COFs also have broad application prospects in the biological field due to their low toxicity and good biocompatibility.In this paper,a series of photosensitive porphyrin-based COFs were successfully prepared,which realized the specific colorimetric detection of radioactive ions in water and effectively inhibited bacterial infection.The main research contents are as follows:1.The method that can visually detect objects without the help of other advanced equipment（colorimetry）has attracted much attention because of its convenience and speed.In this work,a photosensitive porphyrin-based COF（Tph-BDP）with excellent oxidase-mimicking activity was prepared and used as a colorimetric platform for the efficient and sensitive detection of radioactive uranyl ions(UO₂²⁺).Due to its extendedπ-conjugated structure and typical donor-acceptor（D-A）structure,Tph-BDP has narrower energy bandgap and better light absorption properties than monomers and covalent organic polymers（COP）.Under 635 nm laser irradiation,Tph-BDP can activate dissolved oxygen in water to superoxide anion(O₂^?-),which in turn catalyzes 3,3’,5,5’-tetramethylbenzidine（TMB）to form oxidized TMB（ox TMB）with characteristic blue color.In the presence of UO₂²⁺,UO₂²⁺interacts with the imine on ox TMB,resulting in a flocculent precipitate that fades with the characteristic blue color of ox TMB.With the increase of the concentration of UO₂²⁺,the characteristic blue color of ox TMB gradually became lighter and the characteristic absorption gradually weakened.Based on this,a turn-off colorimetric detection platform for UO₂²⁺was constructed.2.The preparation of nanomaterials integrating multiple antibacterial effects is a major challenge in the field of nanomedicine.In this paper,a photosensitive porphyrin-based COF（TAPP-BDP）integrating photodynamic therapy,photothermal therapy and peroxidase therapy was constructed,and the unmodified TAPP-BDP was used for synergistic antibacterial.The low-toxicity TAPP-BDP was synthesized in one step by a traditional solvothermal method,which avoided post-modification or ordered assembly of the material and improved the overall stability of the material.At the same time,due to its extendedπ-conjugated skeleton and typical D-A structure,TAPP-BDP has wider absorption,narrower energy bandgap and better light absorption properties than monomers.Under the irradiation of a single near-infrared light(808 nm,1.5 W cm^-2),TAPP-BDP exhibits excellent photodynamic effect,which can convert O₂ into reactive oxygen species（ROS）for killing bacteria.In addition,TAPP-BDP has broad absorption in the ultraviolet-visible to near-infrared region,manifesting remarkable photothermal properties,which can convert the absorbed near-infrared light into heat,thereby effectively antibacterial.Finally,TAPP-BDP possesses certain mimetic peroxidase（POD）activity,which can convert endogenous H₂O₂ into cytotoxic hydroxyl radicals（·OH）to inhibit bacterial growth.Based on the triple synergy of photodynamic/photothermal/nanozyme,TAPP-BDP exhibited excellent antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus.In vivo studies further demonstrate the excellent biocompatibility and low toxicity of TAPP-BDP,enabling rapid wound healing in infected mice.