Design Of Functionalized Metal-Organic Framework Catalysts And Their Applications In Regulating Product Selectivity Of Organic Reactions

In organic transformation processes,precise control of the product selectivity is crucial for catalysis research.Materials made of metal-organic frameworks（MOFs）are highly structurally modifiable,have regular and organized pore structures,and have a high specific surface area.Although there has been a lot of interest in and rapid development in using the distinctive pore structure of MOF materials to control catalyst performance and improve reaction efficiency,research in this area has advanced relatively slowly because of some restrictions in the structure of MOF materials.This paper focuses on the chemical modification of MOF structures to provide essential catalyst components for catalyst immobilization in order to overcome this issue.It improves the product selectivity of organic transformation reactions by interfering with reaction mass transfer and conversion processes using the pore structure of MOF carrier materials.The following are the specific research contents:（1）Highly selective oxidative cross-coupling of alkynes is catalyzed by MOF-supported copper complexes;these include the downstream Cu complex MIL-101-NH-TMEDACu Cl_x and the MOF-supported N¹,N¹,N²,N²-tetramethylethylenediamine（TMEDA）.The newly developed MIL-101-NH-TMEDA-Cu Cl_x displayed the best catalytic activity and selectivity in the model Glaser heterocoupling reaction when compared to a range of Cu-containing catalysts.It’s interesting to note that,unlike the previously described systems,the Glaser heterocoupling reactions over the MIL-101-NH-TMEDACu Cl_x catalyst can be carried out without the use of external ligands,bases,or acids.The fundamental causes of this system’s remarkable product selectivity are the dense metal catalytic active centers in the pores of MOF materials and their exceptional substrate enrichment capability.（2）Arylamino MOF materials assist in the highly selective synthesis of asymmetrically substituted NH-pyrroles:Utilizing the pore confinement effect in the synthesized amino-modified MOF catalyst Ui O-66-NH₂,the cyclocondensation reaction betweenα-hydroxyketone and 3-aminocrotonate can be efficiently promoted and realize the synthesis of various asymmetrically substituted NH-pyrroles including sutentyrrole intermediates.Compared with a homogeneous catalytic system with a yield of less than 30%,MOF catalysts containing the same active components and with pores of appropriate size can efficiently limit the disordered conversion of substrates and the occurrence of side reactions,thereby achieving higher reaction selectivity and product yield,the yield can reach more than 60%.Compared with previous schemes,the synthesis of asymmetric NH-pyrroles by usingα-hydroxyketone and 3-aminocrotonate as raw materials provides a new strategy for high value-added conversion of biomass.（3）MOFs promote the selective formylation of indole with orthoformate:Although it is theoretically feasible to use orthoformate as a green formylation reagent to synthesize aromatic aldehydes,it is necessary to overcome the relationship between electrophilic products and nucleophilicity in practical applications.Aiming at the triaryl methane compound formed by the adverse reaction in the formylation reaction,this paper proposes a new solution:MOFs materials are used to modify the heteropolyacid catalyst PTA?MIL-100-Cr.This material is able to construct a pore confinement space around the acidic center,thereby effectively suppressing the side reaction that produces triarylmethane.Compared with the previous reaction system,this method has the advantages of low raw material cost,easy acquisition,and less waste generation.In this study,supported catalysts are prepared through chemical modification using the many structural variations and controllable pore diameters of MOFs.Utilizing the carrier’s pore to influence substrate diffusion and reaction processes,it maximizes product selectivity.The development of a new reaction based on this kind of MOF catalyst addresses numerous issues with model organic transformation reactions and offers a workable method for developing a green synthesis system.MOF catalysts are crucial in multi-phase catalytic processes because they effectively increase product selectivity and open up more possibilities for future green synthetic chemistry.