Light-Harvesting Metal-Covalent Organic Frameworks—Atomic-Scale Characterisation for the Design of Photoactive Noble-Metal-Free Materials

Renewable and sustainable energy sources are becoming essential in addressing the growing problem of global warming. In order to decrease the use of non-renewable energy sources, solar technologies to drive chemical reactions represent a significant milestone for the scientific community.^[1] The development of new multifunctional materials that respond to the stimulus of visible light is an ever-growing area of materials chemistry. Recently, photoactive coordination complexes covalently anchored into materials have proven to be a good strategy to improve the molecules' photostability required to efficiently drive photochemical reactions.^[2] Furthermore, researchers have incorporated Co, Ru and Re-based molecules into covalently linked interpenetrated networks, namely metal-covalent organic frameworks (MCOFs), showing excellent performance for both visible-light-driven hydrogen evolution and photoreduction of CO₂, highlighting the potential of these materials for photocatalysis.^[3]Besides, due to their high molecular tunability, supramolecular functionality and excellent structural definition, MCOFs arise as promising materials for enhancing solar-driven reactions.^[4]<br/><br/>Despite a few examples in the literature, the structure control and development of MCOFs are still in an early stage. Due to their complexity and presence of dynamic covalent bonds lead to the formation of nano- and submicron-sized crystals, which are often unsuitable for diffraction, making their atomic-scale characterisation a bottleneck for designing more efficient materials. Moreover, further research is required to explore the use of non-expensive, earth-abundant-based MCOFs.<br/><br/>In this work, a nanoscale characterization of a photoactive Ru-based MCOF designed to reduce CO₂ efficiently under visible light is presented. A combination of experimental and computational techniques will be shown to support without uncertainty the MCOF structure at a nanoscopic level.[5] The atomic mapping obtained from the Ru-based MOCF provided crucial insight for the design and development of a novel earth-abundant Fe-based MCOF analogue. Their characterisation and light-harvesting properties will be also presented.<br/><br/><br/><b>References</b><br/>[1] P. Garrido-Barros, et alI. Funes-Ardoiz, P. Farràs, C. Gimbert-Suriñach, F. Maseras, A. Llobet. <i>Catalytic Oxidation in Organic Synthesis</i>, <b>2017</b>, 63–79.<br/>[2] a) S. Hennessey, C. S. Burke, R. González-Gómez, D. Sensharma, W. Tong, C. Kathalikkattil, F. Cucinotta, W. Schmitt, T. E. Keyes, P. Farràs. <i>ChemPhotoChem</i>, <b>2022</b>, 6 (5), e202100299. b) S. Hennessey, R. González-Gómez, K. McCarthy, C. S. Burke, C. Le Houerou, N. Sarangi, P. McArdle, T. E. Keyes, F. Cucinotta, P. Farràs. <i>ACS Omega</i>, <b>2024</b>, 9 (12), 13872-13882.<br/>[3] a) L. Gutiérrez, V. Martin-Diaconescu, C. Casadevall, F. Oropeza, V. A. de la Peña O’Shea, J. Meng, M. A. Ortuño, J. Lloret-Fillol. <i>ACS Catalysis</i>, <b>2023</b>, 13, 3044–3054. b) W. Han, Y. Liu, X. Yan, Y. Jiang, J. Zhang, Z. Gu. <i>Angew. Chemie Int. Ed.</i>, <b>2022</b>, 61 (40). c) L. Shu-Ying, S. Meng, X. Zou, M. El-Roz, I. Telegeev, O. Thili, T. X. Liu, G. Zhu. <i>Microporous and Mesoporous Materials</i>, <b>2019</b>, 285, 195–201.<br/>[4] Z. Fu, X. Wang, A. M. Gardner, X. Wang, S. Y. Chong, G. Neri, A. J. Cowan, L. Liu, X. Li, A. Vogel, R. Clowes. <i>Chemical Science</i>, <b>2020</b>, 11 (2), 543–550.<br/>[5] S. Hennessey, R. González-Gómez, N. Arisnabarreta, A. Cotti, J. Hou, N. V. Tarakina, A. Bezrukov, K. S. Mali, M. Zaworotko, S. De Feyter, M. García-Melchor, P. Farràs. <b>Submitted</b>.