The Synthesis Of Three-dimensional Metal Organic Frameworks Based On Various Carboxylic Ligands And Their Catalytic And Fluorescent Properties

Owing to the various structures,large surface area,as well as flexible functionalized groups,metal organic frameworks?MOFs?have been widely applied in several aspects such as catalysis,luminescence,gas adsorption and chemical sensing,etc.,becoming the hot topic in the filed of material.Bearing this in mind,this work focuses on the synthesis of classic MOFs with functionalized groups and new MOFs with respect to organic linkers of carboxylic ligands,exploring their catalysis and luminescence properties.The main contents of this work are as follows:1.The catalytic activity of MIL-53 series MOFs in the Strecker reaction was investigated,exploring the influence of metal centers and functional groups in regard to the catalyst as well as the electronic properties and steric hindrance with respect to the substituents of substrates on the reaction.Noteworthy,NH₂-MIL-53?Ga?with Lewis acid-base bifunctional sites show high catalytic activity,good substrate selectivity and universality,which can be reused for 9 runs in recycling experiments.2.The catalytic performance for the catalysts of two isomorphic thiophene-based MOFs?i.e.1-Sc-a and 1-In-a?in Strecker reaction was investigated,exploring the influence of metal sites with respect to catalyst as well as the electronic properties and substituted position in regard to the substituents of substrates on the reaction.In the case of N-benzyl aldimines,both 1-Sc-a and 1-In-a show good catalytic activity and significant substrate universality and selectivity.For N-phenyl aldimines,1-In-a exhibits a better catalytic performance in comparison with 1-Sc-a,while the both two-component and three-component Strecker reaction with the catalyst of 1-In-a were investigated in detail.3.Using semi-rigid ligand of 4,4'-oxybisbenzoic acid,a new Sc?III?-based MOF?2?was synthesized successfully.In the structure of 2,the distorted ligands connect the secondary building units?SBUs?of[Sc₃O?COO?₆?H₂O?₃]alternately,forming the one-dimensional?1D?helical chain.These 1D helical chains stretching along[1,0,0],[1,1,0]and[0,1 0]directions connect each other with connected node of[Sc₃O?COO?₆?H₂O?₃]SBUs,giving a two-dimensional-layered?2D-layered?structure along ab plain.Such 2D-layered structures stack each other with connected node of[Sc₃O?COO?₆?H₂O?₃]SBUs,resulting in a three-dimensional?3D?framework with respect to 2.4.When 4,4'-?1,2-ethynediyl?dibenzoic acid was adopted as organic ligand,a Mn?II?-based MOF?3?was synthesized successfully in regard to new structures.3exhibits pillar-layered 3D framework including compact two-dimensional?2D?inorganic layers and interlayered pillar organic ligands,and these 2D inorganic layers contain COO groups and Mn?II?sites.For the sake of the low coordination number of four with respect to open Mn?II?Lewis acid sites,the acitivated catalyst 3-a shows remarkable catalytic performance in the cyanosilylation of aldehydes or ketones,along with excellent substrate universality and selectivity.In addition,3-a also performs good catalytic performance in Strecker reaction.5.Based on the rigid ligand of[1,1?:4?,1?]terphenyl-3,3?,5,5?-tetra-carboxylic acid?H₄TTCA?,two new MOFs 4 and 5 were synthesized successfully.For 4,neighbouring one-dimensional chains[Ln?-O-HOCO-?₂]_n are connected by TTCA^4-ligands,forming a 3D framework.In the case of 5,neighbouring LnO₈ polyhedrons connect each other with TTCA^4-ligands in coordination mode II,leading to a 1D chain along b axis with rhombus windows.These adjacent 1D chains are further linked by the TTCA^4-ligands in both coordination mode I and II to form a 3D framework in regard with 5.With the 390 nm excitation wavelength,4-Eu,4-Tb and4-Gd show red light,green light and cold white light fluorescence emission,respectively,while only 4-Eu exhibits a fluorescence lifetime of up to milliseconds.In the case of multi-metal doped samples,4-Gd_0.995Eu_0.0025Tb_0.0025 show warm white light emission character under 390 nm excitation wavelength.