Photo-induced processes in multi-component surface-supported metal-organic frameworks – PhotoMOF

We have adopted a strategy of sequential immobilization of photoactive ligands layer by layer (the «layer by layer« technique). This approach allows not only controlling the spatial organization but also the energetic arrangement of components within the SurMOF layer (Surface-anchored Metal Organic Framework), with the aim of creating architectures conducive to directional energy or charge transfer.
The approaches implemented to achieve the objectives of the PhotoMOF program included:
- Synthesis of new photo/redox-active ligands as molecular building blocks for MOF fabrication.
- Development of thin layers of MOFs immobilized on a surface using a «layer by layer« deposition approach, enabling control over the spatial organization of photoactive ligands within the film.
- Study of photo-induced and redox processes in the obtained materials, encompassing light harvesting, energy transfer, electron transfer, and charge-separated states.

An original series of naphthalene-diimide (NDI) and perylene-diimide (PDI) ligands was developed. We demonstrated that once immobilized as thin MOF layers, subtle variations in the NDI ligand structure could play a crucial role in the photophysical properties of the corresponding materials. Supported by theoretical calculations, we could rationalize this phenomenon by a change in the aggregation mode of chromophores within the thin layer, transitioning from non-luminescent to highly emissive films. Photophysical studies allowed us to highlight efficient directional energy transfers within these structures. As a result, the obtained films absorb light energy over a wide range of wavelengths and efficiently emit it as red light.

A future direction of this project is to continue synthesizing photo/redox-active components, especially focusing on a photo-electrocatalytic aspect. The goal is to develop catalysts for proton or CO2 reduction that can be immobilized within a MOF crystalline structure either as elemental building blocks (ligands) or through post-synthetic modification of a MOF structure. This will enable the evaluation of photoelectrocatalytic performance of the obtained electrodes.

[6] “Exploring the Impact of Successive Redox Events in Thin Films of MetalOrganic Frameworks: An Absorptiometric Approach”
V. Monnier, F. Odobel, S. Diring*
J. Am. Chem. Soc., 2023, ja-2023-04114n (10.1021/jacs.3c04114)
[5] “New sulfonated perylene diimide pyrazolate ligands: a simple route toward n-type redox-active hybrid materials”
V. Monnier, F. Odobel, S. Diring*
Chem. Commun., 2022, 58, 9429.
[4] “Photoinduced Delamination of Metal–Organic Framework Thin Films by Spatioselective Generation of Reactive Oxygen Species”
X. Lui, A. Mazel, S. Marschner, Z. Fu, M. Muth, F. Kirschhöfer, G. Brenner-Weiss, S. Diring, F. Odobel, R. Haldar, C. Wöll
ACS Appl. Mater. Interfaces 2021, 13, 57768.
[3] “Antenna Doping: The Key for Achieving Efficient Optical Wavelength Conversion in Crystalline Chromophoric Heterolayers”
R. Haldar*, H. Chen, A. Mazel, D.-H. Chen, G. Gupta, N. Dua, S. Diring*, F. Odobel*, C. Wöll*
Adv. Mater. Interfaces 2021, 8, 2100262.
[2] “Tuning Optical Properties by Controlled Aggregation: Electroluminescence Assisted by Thermally-Activated Delayed Fluorescence from Thin Films of Crystalline Chromophores”
R. Haldar*, M. Jakoby, M. Kozlowska, M. R. Khan, H. Chen, Y. Pramudya, B. S. Richards, L. Heinke, W. Wenzel, F. Odobel, S. Diring*, I. A Howard, U. Lemmer, C. Wöll*
Chem.–Eur. J., 2020, 26, 17016.
[1] “A de novo strategy for predictive crystal engineering to tune excitonic coupling”
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*, C. Wöll*
Nat. Commun. 2019, 10, 2048.

This project aims at developing novel photoactive metal-organic framework (MOF) thin films for solar energy conversion. The innovative aspect of PhotoMOF is based on the controlled and hierarchical integration of multiple photoactive components within the same surface-grown MOF architecture. The main objectives of these new systems are to i) prepare panchromatic light-harvesting antennas, ii) achieve long-lived charge separated states, and iii) ultimately produce solar fuels, such as hydrogen, or reduce carbon dioxide, by combining these redox potentials with suitable electrocatalysts. In-depth photophysical investigation will provide a better fundamental understanding of the energy and electron transfer dynamics at play within these hierarchical hybrid materials.