Application Of Imidazolium Salt Functionalized Metal Organic Porous Materials In Photocatalytic Organic Selective Reaction

Photocatalytic reactions,driven by light under mild conditions,enable precise and efficient material transformation.Compared to traditional catalytic models,this approach is more energy-efficient,eco-friendly,and sustainable.As two predominant classes of metal-organic porous materials,Metal-Organic Cages（MOCs）and Metal-Organic Frameworks（MOFs）boast notable stability,tunable structures,and low toxicity.These advantages have led to their extensive development in photocatalytic carbon dioxide reduction,hydrogen production,and pollutant degradation.Serving as intermediates in photocatalytic reactions,radicals play a pivotal role.Their stability and selectivity are crucial for the precise control of reaction pathways.Leveraging the tunability and unique porous structures of MOCs and MOFs,significant potential exists for the precise manipulation of radicals.However,utilizing metal-organic porous materials to control radicals for photocatalytic organic reactions remains in its nascent stages,necessitating further in-depth exploration and expansion.Imidazolium salts,endowed with functionalities for interaction with anions and gas molecules as well as for charge regulation,have been extensively utilized in the assembly of metal-organic porous materials.This paper elaborates on the construction of MOCs and MOFs through self-assembly of imidazolium salt-based ligands with metals/metal clusters,applied to the effective manipulation of radical intermediates for efficient photocatalytic organic reactions.The main content of this paper is as follows:1.In this chapter,a novel octahedral metal-organic cage MOC-A,featuring twelve imidazole ligands and six nodal points,was constructed through the solvothermal self-assembly of 1,3-bis（4-carboxy-2,6-diisopropylphenyl）-1H-imidazolium chloride salt and a Cu₄ cluster with 4-tert-butylthiolate calix[4]arenesulfonate.MOC-B,with open-framework cavity,was synthesized through the self-assembly of Co₄ clusters using 1,3-bis（4-carboxyphenyl）-1H-imidazolium chloride and 4-tert-butylthio-substituted calix[4]arene sulfone.MOC-A possesses three core advantages:1)The integration of imidazole functional groups into the ligands of metal-organic molecular cages,facilitating the photolysis of N-Cl bonds.2)The encapsulation within an octahedral structure facilitates the folding of linear small-molecular substances.This arrangement allows for precise control over the conformation and stability of the six-membered ring transition state of radicals,thereby enhancing the process of 1,5-HAT.3)Specific pore sizes and cavity volumes exhibit excellent size selectivity for molecular recognition.MOC-A has been applied in the remote unactivated C（sp³）-H sites selective chlorination in amides and sulfonamides.Compared to the MOC-B and parent IPr·HCl,MOC-A exhibits a higher catalytic efficiency（MOC-A:86%yield,MOC-B:45%yield,IPr·HCl:33%yield）.In the C（sp³）-H site-selective reactions involving 42 compounds,including aryl amides,aryl sulfonamides,and trifluoromethyl sulfonamides,MOC-A demonstrated excellent substrate generality（yield up to 98%）.As the substrate chain length increases and volume expands,the catalytic efficiency of MOC-A progressively decreases,demonstrating excellent size selectivity.The catalytic activity of MOC-A did not significantly diminish after seven recycling rounds,indicating its commendable stability and reusability.2.In this chapter,the work involves the construction of a semiconductive metal-organic framework,MOF-A,through solvothermal self-assembly of1,3-bis（3’,5’-dicarboxy-3,5-diisopropyl-[1,1’-biphenyl]-4-yl）-1H-imidazolium chloride salt and Zn I₂.The parent IPr·HCl was combined with Zn（Ph COO）₂ for a homogeneous mediated system,and the synthesis of known metal-organic frameworks MOF-B and MOF-C was based on literature.These three substances were used as references for further studies.MOF-A possesses three core advantages:1)It exhibits a significantly extended range of light absorption wavelengths compared to reference materials,with the absorption edge surpassing 450 nm,demonstrating excellent light-harvesting capabilities.2)It exhibits a shorter transient photoluminescence lifetime（MOF-A=2.03 ns,IPr·HCl+Zn（Ph COO）₂=3.92 ns,MOF-B=8.40 ns,MOF-C=3.72 ns）,demonstrating efficient charge separation.3)The tunable structural characteristics of the MOFs can be strategically adjusted to modulate the reactivity and selectivity of radicals for altering reaction pathways.This enables the facilitation ofα-carbonyl alkyl radical self-coupling reactions,which are typically challenging to achieve within homogeneous systems.MOF-A was employed in the photocatalyticα-carbonyl alkyl radical coupling reaction using vinyloxy pyridinium salts as precursors,exhibiting superior mediating activity（yield up to 93%）.This efficiency significantly surpasses that of homogeneous mixtures,which achieved a maximum yield of 44%.In a series of experiments involvingα-carbonyl alkyl radical self-coupling and cross-coupling reactions with 25 aryl/alkyl substrates,MOF-A demonstrated excellent substrate generality.After eight recycling rounds,MOF-A indicating its commendable stability and reusability.