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Updated: Dec 19, 2025
Author Spotlight: Functionalizing Metal-Organic Frameworks: Advancements, Challenges, and the Power of Post-Synthetic Ligand Exchange
Published on: June 23, 2023
Syntheses and structures of two novel fluorescent metal-organic frameworks generated from a tridentate donor-acceptor
Yong Jin Zhao1, Jian Ping Ma1, Jianzhong Fan2
1College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Molecular and Nano Probes Ministry of Education, Shandong Normal University, Jinan 250014, People's Republic of China.
Abstract:
The tridentate organic ligand 4,4',4''-(4,4,8,8,12,12-hexamethyl-8,12-dihydro-4H-benzo[9,1]quinolizino[3,4,5,6,7-defg]acridine-2,6,10-triyl)tribenzoic acid (H3L) has been synthesized (as the methanol 1.25-solvate, C48H39NO6·1.25CH3OH). As a donor-acceptor motif molecule, H3L possess strong intramolecular charge transfer (ICT) fluorescence. Through hydrogen bonds, H3L molecules construct a two-dimensional (2D) network, which pack together into three-dimensional (3D) networks with an ABC stacking pattern in the crystalline state. Based on H3L and M(NO3)2 salts (M = Cd and Zn) under solvothermal conditions, two metal-organic frameworks (MOFs), namely, catena-poly[[triaquacadmium(II)]-μ-10-(4-carboxyphenyl)-4,4'-(4,4,8,8,12,12-hexamethyl-8,12-dihydro-4H-benzo[9,1]quinolizino[3,4,5,6,7-defg]acridine-2,6-diyl)dibenzoato], [Cd(C48H37NO6)(H2O)3]n, I, and poly[[μ3-4,4',4''-(4,4,8,8,12,12-hexamethyl-8,12-dihydro-4H-benzo[9,1]quinolizino[3,4,5,6,7-defg]acridine-2,6,10-triyl)tribenzoato](μ3-hydroxido)zinc(II)], [Zn2(C48H36NO6)(OH)]n, II, were synthesized. Single-crystal analysis revealed that both MOFs adopt a 3D structure. In I, partly deprotonated HL2- behaves as a bidentate ligand to link a CdII ion to form a one-dimensional chain. In the solid state of I, the existence of weak interactions, such as O-H...O hydrogen bonds and π-π interactions, plays an essential role in aligning 2D nets and 3D networks with AB packing patterns for I. The deprotonated ligand L3- in II is utilized as a tridentate building block to bind ZnII ions to construct 3D networks, where unusual Zn4O14 clusters act as connection nodes. As a donor-acceptor molecule, H3L exhibits fluorescence with a photoluminescence quantum yield (PLQY) of 70% in the solid state. In comparison, the PL of both MOFs is red-shifted with even higher PLQYs of 79 and 85% for I and II, respectively.
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