Design,Assembly and Properties of Chiral Metal-Oragnic Frameworks Based on Biphenol Phosphoric Acids

Author:Chen Xu

Supervisor:cui yong


Degree Year:2018





Metal-organic frameworks(MOFs)as an emerging new class of porous crystalline materials with high porosity and well-defined tunable structures have attracted broad attention for use in heterogeneous asymmetric catalysis.Here,a series of ligands derived from chiral 1,1’-biphenol-derived phosphoric acids that are functionalized with different substituents at the 3,3’-position were designed for MOFs construction.The structures of these chiral MOFs were well characterized,and we have also explored their practical applications in asymmetric catalysis.This thesis includes the following five chapters.In Chapter 1,we briefly introduced the history of MOFs,their advantages compared with traditional materials and the importance of chirality.Next we exemplified the method to synthesizing chiral MOFs and their applications.In Chapter 2,three porous chiral MOFs were prepared from enantiopure phosphono-carboxylate ligands of 1,1’-biphenol that are functionalized with3,5-ditrifluoro-,3,5-difluoro-and 3,5-methylphenyl substituents at the 3,3’-position.For the first time,we show that not only chemical stability but also catalytic activity and stereoselectivity of the MOFs can be tuned by modifying the ligand structures.Particularly,the MOF incorporated with CF3 groups exhibits enhanced tolerances to water,weak acid and base compared with the MOFs with F and Me groups.Under both batch and flow reaction systems,the CF3-containing MOF demonstrated excellent reactivity,selectivity and recyclability,affording high yields and enantioselectivities for alkylations of indoles and pyrroles with a range of ketoesters.In addition,the biphenol ligand functionalized with tert-butyl group at the3,3’-position were designed,and sixteen isostructural MOFs tolerated metal ions with different coordination abilities were got.These obtained MOFs exhibit highly thermal stabilities and good tolerances to water,acids and bases.The presence of open metal sites can act as Lewis acid to catalyze symmetric allylboration,propargylation,Friedel-Crafts alkylation and sulfoxidation with up to 99%ee.The synthetic utilities of the MOF catalysts are demonstrated in the preparation of important building blocks of biological active compounds.Our work provides an approach to achieve single-sited heterogeneous catalysts with high stability,catalytic activity and recyclability by tuning the metal ions.In Chapter 3,three porous chiral MOFs were built by phosphono-carboxylate ligands of 1,1’-biphenol that are functionalized with substituents of different length and steric hindrance at the 3,3’-position.MOF with bulky-anthryl showed excellent stereoselectivity and recyclability in asymmetric condensation/amine addition and hydrogenation reactions for the synthesis of biologically active nitrogen-containing heterocyclic compounds.With the help of postsynthetic ligand exchange method,we got newly MOFs with mixed-ligand,whose catalytic activities further confirmed the importance of bulky substituents.Additionally,computational modeling studies provided the theoretical evidence for the existence of confinement effect of the framework.The synthetic utility of the MOF was shown in the synthesis of DHQZ analogue.In Chapter 4,four isostructural chiral MOFs were build by phosphono-carboxylate ligands of 1,1’-biphenol functionalized with 2,4,6-trimethyl-and 2,4,6-trifluorophenyl substituents at the 3,3’-position with Zn2+,Ba2+and Ca2+.The extstance of 1D channels and potential Lewis acids promoted us to explore their catalytic activities.MOF 7 with 2,4,6-trimethylphenyl in the ligand and Ca2+as node showed excellent catalytic activities in asymmetric hydrogenation reactions.In Chapter 5,a briefly conclusion and outlook were given.