Formation and Encapsulation of Lead Halide Perovskites in Lanthanide Metal–Organic Frameworks for Tunable Emission

Improving the stability of perovskite quantum dots and adjusting their optical properties are essential for their application in advanced optoelectronic equipment. We provide a simple synthetic method to hybridize perovskite quantum dots and metal–organic frameworks (MOFs) into a polymer matrix. The hybrid material is made by encapsulating perovskite CH3NH3PbBr3 quantum dots in lanthanide-based metal–organic frameworks. A series of lanthanide-based metal–organic frameworks (LnMOFs), namely, [Ln­(tpob)­(DMF)­(H2O)]n (Lntpob, Ln = Nd, Sm, Eu, Gd, Tb, Dy, H3tpob = 1,3,5-tris­(4-carbonylphenyloxy)­benzene), have been synthesized under solvothermal conditions and fully characterized. Lntpobs display a three-dimensional (3D) pcu network with central-symmetric [Eu2(COO)4] structural building units (SBUs) linked by one-dimensional (1D) chains. CH3NH3PbBr3@Eutpob hybrids were developed through a three-step process, in which the precursor PbBr2@Eutpob was formed by immersing the Eutpob crystal synthesized in the first step into a PbBr2 solution; then the composite materials could form quickly when CH3NH3Br was added to the precursor. Therefore, the hybrid composite material exhibits luminescent properties related to the excitation wavelength in the form of powders or thin films. In addition, the photoluminescence of the CH3NH3PbBr3@Eutpob composite can be improved and maintained for a long time after it is introduced into the poly­(methyl methacrylate) (PMMA) matrix. Moreover, the emission peak based on the perovskite quantum dots can still maintain about 85% of the original intensity after being left for 30 days. Also, the obtained PMMA films can achieve tunable emission from red to green.

提升钙钛矿量子点（perovskite quantum dots）的稳定性并调控其光学性能，是其应用于先进光电子器件的核心前提。本研究提出一种简便合成策略，可将钙钛矿量子点与金属有机框架（metal–organic frameworks, MOFs）复合至聚合物基体中。该复合材料通过将钙钛矿CH3NH3PbBr3量子点封装于镧系基金属有机框架中制得。一系列镧系基金属有机框架（LnMOFs），其化学式为[Ln(tpob)(DMF)(H2O)]n（命名为Lntpob，其中Ln代表Nd、Sm、Eu、Gd、Tb、Dy，配体H3tpob为1,3,5-三(4-羧基苯氧基)苯），通过溶剂热法合成并得到充分表征。Lntpob呈现出三维（3D）pcu拓扑网络，其结构由中心对称的[Eu2(COO)4]结构构筑单元（SBUs）通过一维（1D）链连接而成。CH3NH3PbBr3@Eutpob复合体系通过三步法制备：第一步合成Eutpob晶体，将其浸入PbBr2溶液中得到前驱体PbBr2@Eutpob；随后向前驱体中加入CH3NH3Br，即可快速得到目标复合产物。因此，该复合粉体或薄膜材料展现出与激发波长相关的发光性能。此外，将CH3NH3PbBr3@Eutpob复合体系引入聚甲基丙烯酸甲酯（PMMA）基体后，其光致发光性能可得到提升并长期维持。该体系中钙钛矿量子点的发射峰在静置30天后仍可保留约85%的初始强度。所制备的PMMA薄膜还可实现从红色到绿色的可调谐发射。