摘要
Metal-organic frameworks(MOFs)and mechanoluminescent(ML)materials have been considered as two types of promising materials that have their own application fields.It would be amazing to endow one material with the advantages of ML and MOFs,thus broadening their applications.However,there are quite few investigations on this topic,and the ML mechanism in ML-MOFs remains unclear.In this study,we proposed a strategy for developing ML-MOFs by doping lanthanide ions into the non-centrosymmetric SBD([Sr(μ-BDC)(DMF)]∞)MOF,and successfully synthesized a series of lanthanide-doped MOFs Ln-SBD(Ln=Tb,Dy,Sm,Eu)and Tb1-xEux-SBD(x=0.2,0.4,0.6,0.8)with multicolor ML.The lanthanide ions were uniformly distributed in the matrix of the SBD-MOF,and occupied the Sr site.The MLMOFs exhibited intense multicolor ML emissions varying from green to yellow to red by changing the co-doping ratios and species of lanthanide ions.The similar ML and photoluminescence(PL)spectra indicated that the ML emission was assigned to the radiative transition from the excited states to the ground states of lanthanide ions.The radiative transition was induced by the electron bombardment process that originated from the piezoelectric effect of the non-centrosymmetric SBD host.In addition,a pioneering temperature sensing research based on ML was carried out,which is promising for realizing dual-functional detection of stress and temperature without excitation light sources.This study gives a unique insight for developing more versatile and interesting smart materials by combining the versatility of MOF with the ML emission,imparting additional values to both MOF and ML materials.Moreover,this study provides a general rule for selecting MOFs with an acentric structure as the host for ML materials.
金属有机框架(MOF)和应力发光(ML)材料被认为是两种有前途的材料,并在诸多领域得到了广泛应用.若能将二者结合起来获得ML-MOF材料,则势必会拓展它们的应用范围.但目前对MLMOF的研究并不多,且其中的ML机制仍不明确.在本研究中,我们提出了一种通过在非中心对称SBD MOF中掺杂镧系离子来开发ML-MOF的策略,成功合成了一系列具有多色应力发光的镧系掺杂MOF Ln-SBD(Ln=Tb,Dy,Sm,Eu)和Tb1-xEux-SBD(x=0.2,0.4,0.6,0.8).镧系离子均匀分布在SBD基质中,并部分占据了Sr的格位.通过改变共掺比例和掺杂种类,ML-MOF表现出了从绿色到黄色再到红色的多色应力发光.相似的ML和PL光谱表明,ML发射与镧系离子从激发态到基态的辐射跃迁有关.辐射跃迁是由电子轰击过程引起的,而电子轰击过程源于非中心对称SBD基质的压电效应.本文首次开展了基于ML的温度传感研究,这有望在没有激发光源的情况下实现应力和温度的双重功能检测.结合MOF的多功能性和ML发射,本研究为开发更多用途、更有趣的多功能材料提供了独特的见解,同时拓展了MOF和ML材料的应用范围.
基金
the National Natural Science Foundation of China(51832005)。
