Luminescent Metal-Organic Frameworks Based On AIE Ligands:Synthesis,Sensing Properties

Metal-organic frameworks?MOFs?,which posess designability and large specific surface area,have been widely applied to many fields,such as gas storage and separation,sensing,catalysis,energy storage,etc.The design and application of the luminescent metal-organic frameworks?LMOFs?have received a great deal of research in the field of sensing,due to its easily functionalized surface and adjustable porosity.In particular,with the development of AIE molecules,AIE-ligand-based LMOFs have attracted more and more attention.In this paper,11new LMOFs based on AIE ligands were successfully prepared by solvothermal method with different carboxylic acid auxiliary ligands and their crystal structures were characterized.Meanwhile,some LMOFs were detailed studied the application in the sensing properties.Its molecular formula is as follows:?1?[Cd?4-L??NDA??H₂O?₂]_n?2?[Cd?4-L??NDA??H₂O?]_n ?3?[Cd_1.5?4-L??NDA?Cl?H₂O?]_n?4?[Cd?4-L?₂Cl₂]_n ?5?[Cd?4-L??2,5-TDC??H₂O?]_n?6?[Cd?4-L??OBA?]_n ?7?[Cd₂?4-L?₂?BDC?₂?0.5 H₂BDC]_n?8?[Cd₂?4-L??BPEA??H₂O?]_n ?9?[Cd?3-L??BDC?_0.5Cl]_n?10?[Cd?3-L??NDA?H₂O]_n?11?[Zn?3-L??NDA?H₂O]_n Where 4-L=9-bis?4-pyridine?ethylene-fluorene;H₂NDA=1,4-naphthalene diformic acid;2,5-TDC=2,5-thiophene dicarboxylic acid;H₂OBA=4,4-diphenyl ether diformic acid;H₂BDC=terephthalic acid;H₂BPEA=4,4-distyrene dicarboxylic acid;3-L=9-bis?3-pyridine?ethylene-fluorene.1.Three new AIE-ligand-based LMOFs 1-3 were successfully prepared from AIE ligand4-L and H₂NDA with three different Cd salts.In 1,the adjacent Cd²⁺ions are bridged with AIE ligand 4-L and NDA^2-to form a?4,4?two-dimensional structure.2 is a two-dimensional plane formed by NDA^2-bridged Cd²⁺,and 4-L is coordinated with Cd²⁺as end ligand.3 is a three-dimensional structure with the Schl?fli symbol(4¹².6³),formed by Cl^-intersection between two different planes.Specially,1 possesses good water stability and exhibits the first luminescence enhancement sensing of Fe³⁺in a water suspension.2.Three LMOFs 4-6 were synthesized with AIE ligand 4-L and different carboxylic acid auxiliary ligands under different reaction conditions.Especially,4 is a two-dimensional structure formed by AIE ligand 4-L bridged Cd²⁺.5 is a one-dimensional straight chain structure formed by bridging{Cd₂O₂?COO?₂}with 2,5-TDC and 4-L is coordinated with Cd²⁺as end ligand.In 6,two-core cluster{Cd₂?COO?₄}connects two OBA^2-forming 1-D double linear chains,and 1-D double linear chains are expanded to a two-dimensional structure through 4-L coordinates with Cd²⁺.The experimental results show that 4-6 have good stability in water,and the three LMOFs have high detection sensitivity towards TNP in aqueous solution.3.Two three-dimensional LMOFs 7-8 were successfully synthesized with AIE ligand 4-L and two different carboxylic acid ligands.In 7,a“Z”two-dimensional plane is formed by the Cd²⁺and BDC^2-,and three-dimensional framework structure is formed by AIE ligand 4-L bridged“Z”planes.In 8,Cd²⁺forms a four-linked three-dimensional structure by four bridged4-L or BPEA^2-.The results showed that 7 and 8 have good stability in water,and exhibit detection for TNP in aqueous solution with high sensitivity,sensitivity and recyclicity.4.Three LMOFs 9-11 were successfully prepared under different conditions by selecting the isomer AIE ligand 3-L of organic molecule 4-L as the main ligand and H₂BDC or H₂NDA as carboxylic acid ligands.The analysis of single crystal structure shows that both 9-11 are two-dimensional structures.In 9,Cd²⁺ions are bridged by Cl^-and BDC^2-to form a two-dimensional structure,and 3-L is coordinated with Cd²⁺on both sides of the plane.In 10,adjacent Cd²⁺ions are bridged with 3-L and NDA^2-to form a?4,4?two-dimensional structure.In 11,two-core cluster{Zn₂O₂?COO?₂}is connected with NDA^2-to form a two-dimensional structure,and 3-L is coordinated with Zn²⁺as end ligand.10-11 have solid luminescence properties.