Design And Synthesis Of Zn(Ⅱ)/Cd(Ⅱ)-Organic Framework Materials With Luminescence Detection Properties

Metal-organic frameworks（MOFs）are porous,high-specific surface area functional materials formed by the connection of metal ions/metal clusters with organic ligand.Luminescent metal-organic frameworks（LMOFs）are increasingly being used to detect harmful contaminants because of their high sensitivity,good selectivity,fast response,easy observation of detection signals,simple operation,low cost,and reusability.Functional organic ligands not only determine the complex and diverse structure of MOFs,but also determine the excellent performance of MOFs.In this paper,9 new LMOFs（2-10）were synthesized by using the fluorene-containing aggregation-induced emission（AIE）-type organic ligand 9-bis（3-pyridine）ethylene-fluorene（3-L）and the ethynylanthracene-containing organic ligand 4-[2-（anthracene-9-yl）ethynyl]pyridine（AEP）ligands as the main ligand,and their crystal structures were determined by a single crystal X-ray diffraction.In terms of detection performance research,1 synthesized in this research group’s previous work and the newly synthesized 2 in this paper were studied in the detection of trivalent metal cations;3-7were studied in the detection of anionic and nitro explosives.The molecular formulas of the10 LMOFs covered in this paper are as follows:（1）[Cd（3-L）（1,4-NDA）（H₂O）]_n;（2）[Zn（3-L）（ISO）]_n;（3）[Cd₂（3-L）（ISO）₂]_n;（4）[Cd（3-L）（ISO）]_n;（5）[Cd（3-L）（2,5-TDC）]_n;（6）[Cd（3-L）₂（2,5-TDC）]_n;（7）[Zn（AEP）₂（2,5-TDC）]_n;（8）[Zn（AEP）₂（HBTC）]_n;（9）[Zn（3-L）（HBTC）]_n;（10）[Cd₂（μ₂-O）（3-L）₂（HBTC）]_n.（H₂ISO=Isophthalic acid;1,4-H₂NDA=1,4-Naphthalenedicarboxylic acid;2,5-H₂TDC=2,5-thiophenedicarboxylic acid;H₃BTC=1,3,5-Benzenetricarboxylic acid）.1、Fluorenyl-containing AIE 3-L-based LMOF materials with efficient detection performance for trivalent metal cations are developed.1 synthesized in our early work has a two-dimensional（2D）structure.The fluorene rings between adjacent layers stack parallel in reverse direction,and the distance of them is 4.19（?）,which reveals weakπ-πinteraction.2also has a 2D structure,but there is noπ-πinteraction between fluorene rings.Both 1 and 2have good luminescence properties in H₂O suspensions.1 can luminescence enhanced efficient detection of Fe³⁺and Bi³⁺in H₂O suspensions.Especially,1 has more sensitive Bi³⁺detection ability because of Bi³⁺with larger ion radius.2 can luminescence quenching efficient detection of Fe³⁺.In particular,1 is the first LMOF-based sensor with luminescence-enhanced aqueous Bi³⁺detection ability.2、Cluster-based LMOF sensor materials are developed by fluorenyl-containing AIE 3-L.Using the same starting materials（3-L,H₂ISO and cadmium nitrate）,two distinct cluster-based Cd（Ⅱ）-organic frameworks 3 and 4 were synthesized by changing the reaction time.In 3,Cd²⁺with two kinds of coordination modes are connected by ISO^2-to form a rare[Cd₄（COO）₈]tetranuclear cluster.Every two clusters are linked by two 3-L and four ISO^2-bridges,which results in a two-dimensional（1D）unique chain with cavities and diamond-shaped channels.Similar to 3,4 also has a 1D chain architecture with cavities and diamond-shaped channels,where every two[Cd₂（COO）₂]²⁺dinuclear clusters are connected by two 3-L and two ISO^2-bridges.Both 3 and 4 have good luminescence properties,and can highly sensitively and selectively detect TNP and MnO₄^-in aqueous medium.Compared with4,3 exhibits more overlap between its emission and the absorption of TNP,which results in higher TNP detection sensitivity for 3.3、Luminescent Cd（Ⅱ）-organic framework sensor materials were developed by fluorenyl-containing AIE 3-L and 2,5-H₂TDC.5 and 6 were solvothermal synthesized to exhibit bifunctional sensing properties.5 has a 6-connected three-dimensional（3D）architecture constructed by[Cd₂（COO）₄]units,2,5-TDC^2-and 3-L bridges.In 6,Cd²⁺is connected by 2,5-TDC^2-and 3-L to form a 2D network.5 and 6 can detect TNP and MnO₄^-in H₂O medium with high sensitivity and selectivity.6 shows better detection performance because of its 2D planar structure.4、Luminescent Zn（Ⅱ）/Cd（Ⅱ）-organic framework sensor materials were developed by novel ethynylanthracene-containing organic ligands.7 and 8 were synthesized by a new ethynylanthracene-containing rigid ligand AEP and carboxyl-containing auxiliary ligands.In7,[Zn₂（COO）₂]²⁺units are linked by 2,5-TDC^2-to form a 2D network,where AEP as terminal ligand coordinates with Zn²⁺,and are distributed on its two sides.Similar to 7,[Zn₂（COO）₂]²⁺units are connected by HBTC^2-to generate a 2D plane for 8.7 has luminescent properties and can sensitively detect TNP and MnO₄^-in H₂O.5、MOFs were constructed by fluorenyl-containing AIE 3-L and 2,5-H₃BTC.9 and 10both exhibit 2D structures.In 9,Zn²⁺ions are linked by pyridyl-N atoms of 3-L to form a"wave-like"chain,and these chains are connected by carboxyl-O atoms of HBTC^2-to form a2D structure.There are two kind of coordination environments for Cd²⁺and two kind of clusters[Cd₂（COO）₂]²⁺and[Cd₂（μ₂-O）₂]in the structure of 10.[Cd₂（μ₂-O）₂]and[Cd₂（COO）₂]²⁺clusters are connected by carboxyl-O atoms of HBTC²to form a 2D plane,and3-L act as terminal ligand and are distributed on two sides of the plane.