(Invited) Innovative MOF-Based Strategies for Assembling Chromophores: Perspectives for Next-Generation Organic Electronics

In the realm of organic electronics, such as photovoltaics, photodetectors, and light-emitting devices, the integration of organic chromophores into solid-state assemblies and their connection with electrodes is crucial. A notable development in this area is the use of metal-organic frameworks (MOFs), also referred to as the MOF method 1, which has been gaining traction. This approach involves using organic chromophores like anthracene and other planar aromatics, including Hexa-peri-hexabenzocoronene (HBC), equipped with coupling units, to create ditopic linkers that connect with metal-oxo nodes in MOFs. In view of the challenges of integrating MOF powders into devices, recent advancements have led to the development of layer-by-layer methods yielding high-quality, monolithic MOF thin films 2. These films offer exceptional optical qualities and show, in many cases, a reduced density of defects. MOFs' periodic structures enable the deliberate design of chromophore assemblies, impacting optical absorption through inter-molecular interactions. This design approach has facilitated the creation of structures like J-aggregates, initially simulated in silico and later realized experimentally 3. Additionally, MOFs enable the realization of band-structure phenomena, such as indirect band gaps 4, and chiroptical effects, including circularly polarized light emission 5 and the helical sensitivity in photodetectors 6. We've also explored lbl architectures for constructing heterostructures, useful in photon up-conversion applications. This involves leveraging MOFs' porous nature, as seen in the integration of C60 into SURMOF pores for applications like photoconductivity 7 and organic diodes 8. Recent efforts have also focused on assembling non-centrosymmetric SURMOFs for nonlinear optical properties, demonstrating substantial second harmonic generation (SHG) activity 9. Our presentation will showcase key instances of successfully incorporating organic chromophores into SURMOFs for device fabrication, emphasizing the synergy with theoretical models. Given the vast number (> 120,000) of known MOFs, a theoretical approach is essential to guide experimental efforts efficiently. References: 1 R. Haldar, L. Heinke, Ch. Wöll, Advanced Materials (2020), Adv. Mater., 2020, 32, 1905 2 L. Heinke, Ch. Wöll, Adv. Mater., 2019, 31 (26), 1970184 3 J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Coupry, M. Addicoat, S. Yoneda, Y. Tsuitsui, T. Sakurai, S. Seki, Z. Wang, P. Lindemann, E. Redel, Th. Heine, Ch. Wöll, Angew. Chemie Int. Ed. 54, 7441 (2015) 4 R. Haldar, A. Mazel, M. Krstic, Q. Zhang, M. Jakoby, I. A. Howard, B. S. Richards, N. Jung, D. Jacquemin, S. Diring, W. Wenzel, F. Odobel, Ch. Wöll, Nat. Comm., 10, 2048 (2019) 5 Y.H. Xiao, P. Weidler, S.S. Lin, C. Wöll, Z.G. Gu, J. Zhang, Adv. Functional Materials 32 (34), 2204289, (2022) 6 Y.-B. Tian, K. Tanaka, L.-M. Chang, C. Wöll, Z.-G. Gu and J. Zhang, Nano Letters 2023, 23 5794 7 X. Liu, M. Kozlowska, T. Okkali, D. Wagner, T. Higashino, G. Brenner-Weiß, S. M. Marschner, Z. Fu, Q. Zhang, H. Imahori, S. Bräse, W. Wenzel, C. Wöll, L. Heinke, Angew.Chem.Int. Ed. 2019, 58, 9590 8 A. Chandresh, X. Liu, Ch. Wöll, L. Heinke, Adv. Sci., 2021 , 8, 2001884 9 A. Nefedov, R. Haldar, Z. Xu, H. Kühner, D. Hofmann, D. Goll, B. Sapotta, S. Hecht, M. Krstić, C. Rockstuhl, W. Wenzel, S. Bräse, P. Tegeder, E. Zojer, Ch. Wöll, Adv. Mat. 2103287 (2021)