Metal-organic frameworks (MOFs) are a family of highly porous materials, which are composed of metal-based nodes and organic ligands. Thanks to the large surface areas and tunable chemical functionalities, MOFs are emerging as excellent catalysts for the sector of renewable energy. Of particular interest, the structures of certain MOFs are highly flexible, allowing for reversible structural transitions upon the stimuli from various external sources. Such stimuli-responsive behaviors of MOFs create new opportunities to design functional materials for switchable catalysis. Nevertheless, the exploration of the flexible MOF-based catalysts is still at a nascent stage. Herein, to advance the fundamental understanding of how the dynamic behaviors of flexible MOFs could affect the catalytic performance, first-principles calculations were carried out using the density functional theory, where a bimetallic MOF, MIL-88B(Fe/Co), was selected as a model structure. Results showed that the lattice contraction can result in twisted ligands as well as the rotary metal nodes, which subsequently lead to variations of the free energy diagrams for the oxygen evolution reaction, demonstrating the critical role of structural flexibility in determining the energy barriers during the elementary steps. Further analysis using the pair distribution function and electron localization function confirmed the rigid short-range order of MOFs during the structural transitions, as well as the tunable guest-host interactions upon lattice contraction/expansion, which could be responsible for the observed differences in the energy barriers during catalysis. Overall, the findings from this work offer new insights into the catalyst design for the modulated production of renewable fuels.Reference: CrystEngComm, 2023, 25, 6441 - 6448