Ab-initio Raman simulations of metal-organic-frameworks

Abstract

Metal-organic frameworks (MOFs) are reticular materials composed of metal centers connected to organic linkers. Among the many materials suitable for CO2 capture and storage (CCS), MOFs stand out as a promising candidate due to their large pore volume, high surface area, high CO2 selectivity, and chemical tunability [1]. In this scenario, Raman spectroscopy has been widely used to understand the molecular composition, structure, and interactions within molecular materials [2]. For MOFs, their Raman spectra consist of vibrational modes of the ligand molecules, metal-ligand bonds, and phonon modes of the lattice. Thereafter, structural analysis can provide useful information regarding changes in coordination, bond strength, and the overall structure of MOFs . On the other hand, a theoretical approach to simulating vibrational properties can aid in benchmarking theoretical models and interpreting experimental spectra, as simulations can provide information that is not accessible experimentally and consequently support in spectral assignment, for instance. Although some studies have conducted experimental analysis of vibrational spectra with theoretical support [3], few works have delved into ab-initio simulations of Raman spectroscopy for MOFs. In this work, we explore first-principles Raman simulations of different MOFs, aiming to elucidate important features that contribute to obtaining reliable spectra. We demonstrate that carefully verifying the experimental structure prior to simulation is essential, as the spectra are highly sensitive to geometry. The simulations were performed using the density-functional-theory-based code CP2K [4], and the theoretical results were compared with experimental data. References [1] T. Ghanbari, F. Abnisa, W. Mohd and A. Wan Daud. A review on production of metal organic frameworks (MOF) for CO2 adsorption. Science of The Total Environmen 707, 135090 (2020). [2] J. Sunil, C. Narayana, G. Kumari and K. Jayaramulu. Raman spectroscopy, an ideal tool for studying the physical properties and applications of metal–organic frameworks (MOFs). Chem. Soc. Rev. 52, 3397-3437 (2023) [3] A. E. J. Hoffman, L. Vanduyfhuys, I. Nevjestić, J. Wieme, S. M. J. Rogge, H. Depauw, P. Van Der Voort, H. Vrielinck, and V. Van Speybroeck. Elucidating the Vibrational Fingerprint of the Flexible Metal–Organic Framework MIL-53(Al) Using a Combined Experimental/Computational Approach. The Journal of Physical Chemistry C 122 (5), 2734-2746 (2018). [4] T. D. Kühne et al. CP2K: An electronic structure and molecular dynamics software package - Quickstep: Efficient and accurate electronic structure calculations. The Journal of Chemical Physics 152(19), 194103 (2020).