The Synthesis And Properties Of Eu²⁺ Doped SSZ-39 Zeolite

Zeolite are crystalline inorganic materials with regular channels or cavities.There are many kinds of zeolite frameworks,and the preparation is simple and stable.Usually the basic structural characteristic unit of the framework is the TO₄ tetrahedron(T=Si⁴⁺,Al³⁺,etc.).It has excellent structural stability and has important applications in many fields.Among them,the eight elemental ring（8MR）zeolite materials,the two most prominent catalytic applications are methanol to olefins（MTO）and selective catalytic reduction（SCR）of NOx in exhaust gases.As one of them,SSZ-39zeolite has an AEI topology and is an aluminosilicate microporous material.Excellent catalytic activity and hydrothermal stability have been shown in these two catalytic reactions.In this paper,first focuses on the factors such as silicon aluminum source,crystallization temperature,crystallization time and seeding on the synthesis of zeolites were studied in detail for the synthesis of SSZ-39 zeolites.Explore the best synthetic method for synthesizing SSZ-39 zeolites.Then,using the prepared SSZ-39zeolite as the matrix,the luminescent material of Eu²⁺as the luminescent center was discussed,and the structure of the zeolite was further studied.The specific contents are as follows:（1）The OSDA N,N-dimethyl-3,5-dimethylpiperidinium used to prepare SSZ-39zeolite was first synthesized and characterized by elemental analysis,high resolution mass spectrometry and proton NMR.The results indicate that it can be used to prepare the series of SSZ-39 zeolite samples.The series of SSZ-39 zeolite samples were synthesized by hydrothermal method and characterized by XRD and SEM.The experimental results were compared and analyzed.It was found thatN,N-dimethyl-3,5-dimethylpiperidinium as the OSDA,Y30 zeolite as a silicon aluminum source at170°C and Y10 zeolite and ludox as silicon at 180°C.TheSSZ-39 zeolite was successfully synthesized.It is worth noting that the Y30 zeolite is used as the silicon aluminum source,and a small amount of SSZ-39 zeolite is used as the seed crystal,and the single phase of the SSZ-39 zeolite can be synthesized in only three days.（2）The pores and cages of the zeolite structure provide an ideal microenvironment for isolating the luminescent center.By ion exchange of SSZ-39 zeolite and subsequent heat treatment in a reducing atmosphere,a novel luminescent material was obtained.Eu²⁺ions doped SSZ-39 zeolite with tunable emission.The doped Eu²⁺ions are isolated by a three-dimensional cage connected in the zeolite,providing a stable environment for the luminescent center.The phases and structures of Eu²⁺-SSZ-39samples were analyzed by XRD,SEM and TG-DSC.The sample was ion-exchanged and kept at 800°C for 4 hours under a reducing atmosphere,the zeolite still maintained the original framework structure and still retained the original particle morphology.Also,the sample can maintain its original structure in the temperature range of 25-1000°C and has good thermal stability.By testing the PL spectrum of the Eu²⁺-SSZ-39 sample,it was observed that the Eu²⁺doped SSZ-39 sample has a broad excitation band and a strong blue emission.And the tunable emission can be obtained by simply adjusting the ion exchange time.It was found to have good thermal stability by testing the thermal quenching performance of the Eu²⁺doped SSZ-39 sample.And the emission peak position of the sample hardly moved as the temperature increased.It shows the potential application of Eu²⁺-SSZ-39 in LED phosphors.