Multiple Interpenetrating Metal–Organic Frameworks with Channel-Size-Dependent Behavior for Selective Gossypol Detection and Perovskite Quantum Dot Encapsulation

An interpenetrating structure endows metal–organic frameworks (MOFs) with many exciting applications, such as fluorescence detection and host–guest chemistry. Herein, two unique structure-interpenetrating In-MOFs (In-pdda-1 and In-pdda-2; H2pdda = 4,4′-(pyridine-2,5-diyl)dibenzoic acid) are constructed by different coordination configurations. The four-connected In3+ center shows a triangular-pyramidal configuration or a 2D rectangle, forming an unc topology for In-pdda-1 and a sql network for In-pdda-2, respectively. Two different interpenetrating modes created by linear rigid ligands and metal clusters are observed in the two MOFs (In-pdda-1, 8-fold interpenetrating mode; In-pdda-2, [2D + 2D] interpenetrating mode), which determine the channel-size-dependent properties in fluorescence applications. During the quantitative detection process of gossypol, the small rhombic channels divided by interpenetrating molecular planes of In-pdda-2 greatly limit the distance between the analyte and the probe, promoting electron transfer and energy transfer processes and thus resulting in a low detection limit (28.6 nM). In addition, the pore size effect of In-pdda-1 encouraged us to explore an in situ perovskite quantum dot encapsulation strategy to obtain a MAPbBr3@MOF material with tunable and stable luminescence properties. Both of the above channel-size-dependent fluorescence properties may provide inspiration for the structural design and specialized applications of MOF materials.互穿结构赋予金属有机框架（metal–organic frameworks, MOFs）诸多极具应用潜力的应用方向，例如荧光检测与主客体化学。本文中，研究者通过不同配位构型构筑了两款独特的结构互穿型铟基金属有机框架（In-MOFs，即In-pdda-1与In-pdda-2；其中H₂pdda代表4,4'-(吡啶-2,5-二基)二苯甲酸）。四连接的三价铟中心分别呈现三角锥配位构型与二维矩形配位结构，进而分别为In-pdda-1构建出unc拓扑结构，为In-pdda-2构建出sql网络。两款MOFs中存在两种由线性刚性配体与金属簇构筑的不同互穿模式（In-pdda-1为八重互穿模式；In-pdda-2为[2D+2D]互穿模式），该结构特征决定了两款材料在荧光应用中表现出通道尺寸依赖的性能。在棉酚的定量检测过程中，In-pdda-2的互穿分子平面所分隔出的小型菱形通道，极大缩短了分析物与探针之间的距离，促进了电子转移与能量转移过程，最终实现了28.6 nM的极低检测限。此外，In-pdda-1的孔径效应启发我们开发了原位钙钛矿量子点封装策略，以此制备得到具有可调谐且稳定发光性能的MAPbBr3@MOF复合材料。上述两款MOFs所展现的通道尺寸依赖型荧光性能，可为MOF材料的结构设计与特定应用提供设计思路与参考借鉴。