Room Temperature Phosphorescence Of Zn(?) Based On Coordination Polymers Host-guest

In the last few years,room temperature phosphorescent materials have aroused much concern due to their potential for optoelectronic applications.Generally speaking,most of the previous room temperature phosphorescent materials contain heavy metals and precious metals,resulting in poor stability,potential toxicity and high cost.These shortcomings have largely limited their practical applications.Therefore,it is vital to develop new room temperature phosphorescent materials of cheap,energy-saving and no environmental pollution.Coordination polymers are crystalline materials formed by metal salts and organic molecules.In the structure of coordination polymer,the effective interaction between molecules plays a certain role in restraining the intramolecular vibration,which can lock the molecular conformation to promote the generation of triplet excitons and improve the phosphorescence performance.Due to the diversity and adjustability of coordination polymers,the room temperature phosphorescence performance of coordination polymers can be achieved by introducing different chromophore ligands,metal ions and guest molecules(such as dyes,metal nanoparticles,Quantum dots)into the pores or crystal matrix.Taking all of above into accounts,in this paper we designed and synthesized three coordination polymer-based room temperature phosphorescent materials with high stability and excellent luminescence performance through a simple method.By studying the configuration and stacking mode of luminescent molecules,the structure-activity relationship between the structure of coordination polymers and room temperature phosphorescence properties was revealed.By encapsulating guest molecules into coordination polymer matrix or array,the emission color of phosphorescent can be regulated and the light-trapping ability can be enhanced.Besides,the photoelectric properties were studied.The primary coverage is as follows:1.The micro-nano-scale coordination polymer{Zn(IPA)}(IPA=iso-phthalic acid)can be obtained by rapid precipitation in water,and it exhibits high-efficiency room temperature phosphorescent performance and phosphorescence lifetime reach 926 ms at room temperature.Using this method,the in situ encapsulation of rhodamine B into the coordination polymer matrix can expressly tune the phosphorescence emission color from green to red(lifetime is 450 ms),enhancing the ability of solar energy-harvesting,charge carrier separation efficiency and photoelectron performance.The study found that there is a significant overlap between the UV absorption of Rhodamine B and the phosphorescence emission spectrum of the coordination polymer,indicating that phosphorescence energy transfer can occur.The photoelectric test shows that under the condition of bias voltage and light,the charge transfer and the separation efficiency of photoinduced charge-hole can be greatly promoted,and the photoelectric performance can be improved.2.An ionic coordination polymer{[Zn_0.5(BMP)(H₂O)]NO₃}was synthesized by semi-rigid organic ligand 3,5-bis(1-imidazol)pyridine(BMP)and Zn²⁺.The synthesized coordination polymer exhibits long lasting phosphorescence lifetime,which is 6400 times than the original BMP phosphorescence ligand.Theoretical calculations show that the counterion NO₃^-enormously affects the electronic structure and energy level of the cationic coordination polymer.Eosin Y(EY)dye was encapsulated in{[Zn_0.5(BMP)(H₂O)]NO₃}by simple anion exchange,and host-guest material(EY@{[Zn_0.5(BMP)(H₂O)]NO₃})was obtained.The phosphorescence color is adjusted from yellow to rare near-infrared emission through effective phosphorescent energy transfer.We also studied the photoelectric properties of{[Zn_0.5(BMP)(H₂O)]NO₃}and EY@{[Zn_0.5(BMP)(H₂O)]NO₃}.3.Two phosphorescence ligands iso-phthalic acid(IPA)and 2-methylimidazole(MIM)were selected to construct an nonporous coordination polymer{Zn(IPA)(MIM)₂}with long-lived phosphorescence lifetime up to 552 ms.By the doping of Eosin Y(EY)dye molecules under an in situ process,the phosphorescence emission color of{Zn(IPA)(MIM)₂}can be expressly tuned from green to red.The light-harvesting range can also be vastly broaden from UV to visible region.Photoelectron measurements reveal that the synergistic effect of bias voltage and illumination can restrain electron-hole recombination for the generation of more free charges.