Construction Of Strongly Sensitizing UiO-MOF Photocatalysts For Photosynthesis

The efficient conversion of solar energy into chemical energy through photosynthesis is one of the effective ways to meet future energy demand and solve environmental pollution problems.In artificial photosynthesis,photocatalysts play essential roles in capturing light,separating and transferring energy/electrons,and are a crucial factor that determines the overall efficiency of the process.Therefore,the development of photocatalysts with strong sensitization is of great significance to achieve efficient photosynthesis.UiO-MOFs are widely used in photocatalysis research as porous crystalline materials with well-defined structures,diverse types,exceptional stability,customizable surface functionalities,and convenient adjustability.However,the conventional UiO-MOFs photocatalysts generally have weak sensitization ability,which is not conducive to the efficient capture and conversion of solar energy.To solve this problem,we functionalized the ligands and clusters of MOFs at the molecular level and developed a series of highly sensitive UiO-MOFs photocatalysts.The main contents of the paper are as follows:（1）A series of strongly sensitized Cu-based MOFs photocatalysts（Cu-MOFs）were developed by introducing copper complexes into UiO-MOFs ligands using the ligand modification strategy.By changing the blocking group of phenanthroline ligand in copper complexes,the coordination environment of the copper sensitization center was effectively adjusted,leading to a significant enhancement in the photosensitization capability of the MOFs.The yield of N-benzylbenzylideneamine was up to 90.2%with Cu-5-MOF as photocatalyst,which was 11 times higher than that of Cu-1-MOF（8.2%）.In addition,Cu-5-MOF can be recycled and reused for over 5 times without the obvious activity loss,representing a robust photochemical stability.The results show that the introduction of copper complexes with large steric functional groups can effectively increase torsional resistance and reduce the excitation loss of MOF photocatalysts,resulting in its advantages in strong visible light absorption,efficient electron-hole separation and good photochemical stability,which greatly contributed to boosting photosynthesis.This work opens a new horizon for the development of highly efficient and earth-abundant MOF photocatalysts by restricting the excited state configuration at a molecular level.（2）The high-nuclear cobalt cluster nodes with strong sensitization were constructed,which replaced the traditional six-nuclear metal cluster nodes represented by Zr₆ cluster.Furthermore,a series of high-nuclear UiO-MOFs(Co₁₆-MOFs)with photoactivity were developed by introducing a variety of light-absorbing ligands.By taking advantage of the rich coordination modes and strong coordination ability of N₃^-and HCOO^-,stable hexadecameric cobalt azide clusters were constructed as the nodes of MOFs.Furthermore,Co₁₆ clusters were capable of coordinating and assembling with organic ligands possessing various functionalities and lengths to construct a series of novel UiO-MOFs.The results showed that Co₁₆-MOF-BDC could harvest visible light for driving benzylamine coupling reaction.The catalytic yield of N-benzylbenzylideneamine was 47.5%by Co₁₆-MOF-BDC,which was 7times higher than that of the conventional Zr-UiO-MOF.Moreover,the introduction of amino functional group increased the absorption channels of the catalyst and promoted the electron-hole separation efficiency,resulting in an increase of the yield to 100%.This work improves the photosensitization ability of MOFs by precisely constructing high-nuclear cluster nodes,which provides a scientific reference for the development of efficient MOFs photocatalysts.（3）By using a Click reaction,the Bodipy chromophore,which has strong visible light absorption,was coupled to the azide group present on the surface of the high-nuclear cobalt cluster.Consequently,a novel UiO-MOFs photocatalyst,called Bodipy@Co₁₆-MOF-BDC,was developed.Bodipy@Co₁₆-MOF-BDC can efficiently drive the benzylamine coupling reaction,exhibiting a catalytic yield of 100%,which is 3 times higher than that of Co₁₆-MOF-BDC.Systematic studies showed that Bodipy units could significantly enhance the capture of visible light and the electron-hole separation of the photocatalysts,ultimately leading to a significant enhancement in photosynthesis efficiency.This work provides an important scientific reference for photosensitization of MOFs nodes.（4）UiO-MOFs were introduced with photoactive organic ligands that could produce and store singlet oxygen to achieve light energy storage and on-demand release.In this chapter,a mixed-ligand co-coordination strategy was developed to integrate the photosensitizing unit and singlet oxygen storage unit into the UiO-MOF framework（UiO-DPA-Se）using a one-pot method.The MOF framework integrates photosensitizing,singlet oxygen generation,storage and release functions into a single entity.The results showed that the UiO-DPA-Se can effectively generate singlet oxygen under the excitation of visible light,and oxidize dihydroartemisinin into higher value artemisinin.At the same time,it can store abundant singlet oxygen to generate endoperoxide MOFs（UiO-Se-EPOs）.The stored reactive oxygen species were released under heating conditions.Importantly,the production,storage and release of singlet oxygen from the UiO-DPA-Se could be recycled more than five times,demonstrating the good photostability and fatigue resistance of the photosensitive MOF.This work provides a new idea for the storage and utilization of sunlight.