Biological iron-sulfur (Fe-S) enzymes drive key reactions, including fuel production from renewable feedstocks, e.g., CO₂ and H₂O (Fig. 3a). While synthetic Fe-S clusters hold promise as catalytic mimics, their instability outside enzyme scaffolds limits their practical applications. This study presents a novel strategy to stabilize Fe-S clusters by embedding them into one-dimensional (1D) coordination polymers, mimicking enzyme scaffolds. This approach enhances cluster stability and catalytic longevity, enabling transformations that remain globally inaccessible.
We synthesized polymers composed of linear chains of [4Fe-4S] clusters bridged by organic linkers (Fig. 3b). These structures rigidly anchor the clusters, preventing decomposition due to linker loss or bimolecular reactions. This stabilization improves both hydrolytic and redox durability, as well as catalytic activity in hydrogen production. Cluster C was incorporated into two polymer variants, P_S and P_L, containing shorter and longer organic linkers, respectively. The structure of P_L was confirmed via powder X-ray diffraction (Fig. 3c).
To evaluate catalytic performance, we tested polymers P_L and P_S and free cluster C for H₂ production using cyclic voltammetry. A large current response increasing with acid concentration confirmed that polymerization preserved catalytic function. Foot-of-the-wave analysis revealed that P_L exhibited catalytic activity 5× higher than C and 20× higher than P_S. We attribute this enhancement in P_L to its longer linker, increased flexibility, and improved stability, which facilitate faster substrate diffusion and the generation of active intermediates.
This work demonstrates that polymeric encapsulation stabilizes Fe-S clusters while maintaining reactivity, providing a platform for their use in sustainable catalytic applications.

Andrew Ritchhart

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