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1. Natural Assembly of Electroactive Metallopolymers on the Electrode Surface: Enhanced Electrocatalytic Production of Hydrogen by [2Fe–2S] Metallopolymers in Neutral Water

   https://doi.org/10.1021/jacs.3c03379  

   Clary, Kayla E.; Gibson, Arthur C.; Glass, Richard S.; Pyun, Jeffrey; Lichtenberger, Dennis L. (June 2023, Journal of the American Chemical Society)

   A molecular catalyst attached to an electrode sur-face can in principle offer the advantages of both homogeneous and heterogeneous catalysis. Unfortunately, some molecular catalysts constrained to a surface lose much or all of their solution performance. In contrast, we have found that when a small molecule [2Fe–2S] catalyst is incorporated into metallopolymers of the form PDMAEMA–g–[2Fe–2S] (PDMAEMA = poly(2-dimethylamino)ethyl methacrylate) and adsorbed to the sur-face, the observed rate of hydrogen production increases to kobs > 105 s-1 per active site with lower overpotential, increased life-time, and tolerance to oxygen. Herein, the electrocatalytic performances of these metallopolymers with different length polymer chains are compared to reveal the factors that lead to this high performance. It was anticipated that smaller metallopolymers would have faster rates due to faster electron and proton transfers to more accessible active sites, but the experiments show that the rates of catalysis per active site are largely independent of the polymer size. Molecular dynamics modelling reveals that the high performance is a consequence of adsorption of these metallopolymers on the surface with natural assembly that brings the [2Fe–2S] catalytic sites into close contact with the electrode surface while maintaining exposure of the sites to protons in solution. The assembly is conducive to fast electron transfer, fast proton transfer, and a high rate of catalysis regardless of polymer size. These results offer a guide to enhancing the performance of other electrocatalysts with incorporation into a polymer that provides optimal interaction of the catalyst with the electrode and with solution. 

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2. Rapid design of top-performing metal-organic frameworks with qualitative representations of building blocks

   https://doi.org/10.1038/s41524-023-01125-1  

   Comlek, Yigitcan; Pham, Thang Duc; Snurr, Randall Q.; Chen, Wei (December 2023, npj Computational Materials)

   Abstract Data-driven materials design often encounters challenges where systems possess qualitative (categorical) information. Specifically, representing Metal-organic frameworks (MOFs) through different building blocks poses a challenge for designers to incorporate qualitative information into design optimization, and leads to a combinatorial challenge, with large number of MOFs that could be explored. In this work, we integrated Latent Variable Gaussian Process (LVGP) and Multi-Objective Batch-Bayesian Optimization (MOBBO) to identify top-performing MOFs adaptively, autonomously, and efficiently. We showcased that our method (i) requires no specific physical descriptors and only uses building blocks that construct the MOFs for global optimization through qualitative representations, (ii) is application and property independent, and (iii) provides an interpretable model of building blocks with physical justification. By searching only ~1% of the design space, LVGP-MOBBO identified all MOFs on the Pareto front and 97% of the 50 top-performing designs for the CO₂working capacity and CO₂/N₂selectivity properties. 

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3. Scutoids as Building Blocks for Topologically Interlocking Material Systems

   https://doi.org/10.1002/adem.202400270  

   Ballance, Tanner; Siegmund, Thomas (April 2024, Advanced Engineering Materials)

   Topologically interlocking material (TIM) systems are constrained assemblies of building blocks with geometry such that individual unit elements cannot be removed from the assembly without complete disassembly. These assemblies can bear load in the absence of adhesive bonds. TIM systems with scutoid‐shaped building blocks are investigated. Scutoids are prism‐like shapes with two polygonal faces and contain vertices on the lateral sides which enable geometric interlocking. The quasi‐static mechanical behavior of two types of scutoid‐based TIM systems is investigated and compared to reference tetrahedron‐based TIM systems. TIM systems are realized as plate‐type assemblies and a central point‐force load is considered. The computational analysis is conducted with the finite‐element method. Scutoid‐based TIM systems are found, in aggregate, to match or exceed the performance of the tetrahedra‐based systems. It is documented that TIM systems in general, but scutoid‐based systems in particular, emerge to possess chiral characteristics. The combination of building block symmetry and assembly symmetry together determines the type of chirality in the mechanical response. Experimental data validates the computational finding. In summary, considering scutoids as building blocks for load‐carrying TIM assemblies opens the pathway to new classes of mechanical behavior in systems where structure and microstructure strongly interact with each other. 

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4. Diiron Disulfide Methacrylate Metallopolymers as Sustainable Electrocatalysts for Water-Splitting and Molecular Hydrogen Production

   https://doi.org/10.1021/acsmacrolett.5c00567  

   Gibson, Arthur C; Glass, Richard S; Lichtenberger, Dennis L; Pyun, Jeffrey (October 2025, ACS Macro Letters)

   Rowan, Stuart J (Ed.)

   ABSTRACT: We review in this Viewpoint recent progress on the development of a new class of sustainable electrocatalytic systems for water-splitting and molecular hydrogen generation using diiron disulfide ([2Fe-2S]) active site methacrylate metallopolymers. To date, noble metal catalysts (e.g, platinum) remain the best electrocatalysts for molecular hydrogen generation using water as the chemical feedstock and proton donor. However, there remains a need for the synthesis of efficient electrocatalytic systems using low cost, earth abundant materials for sustainable H2 generation. We focus on our recent work in this area using well-defined single site [2Fe-2S]-metallopolymer catalysts. Thus far, these systems have demonstrated rates of hydrogen production >25 times faster than [FeFe]-hydrogenase enzymes and match the current densities of platinum with only 0.2 V higher potential when operating in water at neutral pH with tris(hydroxymethyl)aminoethane (TRIS) buffer (Faradaic yields 100±3%). The molecular design and synthesis of [2Fe-2S]-metallopolymers are reviewed along with mechanistic studies unraveling the causality of efficient H2 production from this catalytic system. The overall current output and overpotential are improved by (a) the reversible electrostatic adsorption of the metallopolymer on the carbon electrode surface that enhances the proton and electron transfer rates and (b) the use of protic buffer electrolytes (PBEs) that enhance the availability of protons. The schemes summarized here to improve the performance of [2Fe-2S] catalysts by incorporation into metallopolymers may be used to enhance the performance of other molecular electrocatalysts at the electrode surface. 

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5. Catalytic Metallopolymers from [2Fe-2S] Clusters: Artificial Metalloenzymes for Hydrogen Production

   https://doi.org/10.1002/ange.201813776  

   Karayilan, Metin; Brezinski, William P.; Clary, Kayla E.; Lichtenberger, Dennis L.; Glass, Richard S.; Pyun, Jeffrey (April 2019, Angewandte Chemie)

   Reviewed herein is the development of novel polymer‐supported [2Fe‐2S] catalyst systems for electrocatalytic and photocatalytic hydrogen evolution reactions. [FeFe] hydrogenases are the best known naturally occurring metalloenzymes for hydrogen generation, and small‐molecule, [2Fe‐2S]‐containing mimetics of the active site (H‐cluster) of these metalloenzymes have been synthesized for years. These small [2Fe‐2S] complexes have not yet reached the same capacity as that of enzymes for hydrogen production. Recently, modern polymer chemistry has been utilized to construct an outer coordination sphere around the [2Fe‐2S] clusters to provide site isolation, water solubility, and improved catalytic activity. In this review, the various macromolecular motifs and the catalytic properties of these polymer‐supported [2Fe‐2S] materials are surveyed. The most recent catalysts that incorporate a single [2Fe‐2S] complex, termed single‐site [2Fe‐2S] metallopolymers, exhibit superior activity for H2 production. 

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