Substrate-Dependent Conformational Switch of the Noncubane [4Fe-4S] Cluster in Heterodisulfide Reductase HdrB

Ionic Covalent Organic Framework Solid-State Electrolytes

Rechargeable secondary batteries, widely used in modern technology, are essential for mobile and consumer electronic devices and energy storage applications. Lithium (Li)-ion batteries are currently the most popular choice due to their decent energy density. However, the increasing demand for higher energy density has led to the development of Li metal batteries (LMBs). Despite their potential, the commonly used liquid electrolyte-based LMBs present serious safety concerns, such as dendrite growth and the risk of fire and explosion. To address these issues, using solid-state electrolytes in batteries has emerged as a promising solution. In this Perspective, recent advancements are discussed in ionic covalent organic framework (ICOFs)-based solid-state electrolytes, identify current challenges in the field, and propose future research directions. Highly crystalline ion conductors with polymeric versatility show promise as the next-generation solid-state electrolytes. Specifically, the use of anionic or cationic COFs is examined for Li-based batteries, highlight the high interfacial resistance caused by the intrinsic brittleness of crystalline ICOFs as the main limitation, and presents innovative ideas for developing all- and quasi-solid-state batteries using ICOF-based solid-state electrolytes. With these considerations and further developments, the potential for ICOFs is optimistic about enabling the realization of high-energy-density all-solid-state LMBs.

DsrMKJOP is the terminal reductase complex in anaerobic sulfate respiration

Microbial dissimilatory sulfate reduction (DSR) is a key process in the Earth biogeochemical sulfur cycle. In spite of its importance to the sulfur and carbon cycles, industrial processes, and human health, it is still not clear how reduction of sulfate to sulfide is coupled to energy conservation. A central step in the pathway is the reduction of sulfite by the DsrAB dissimilatory sulfite reductase, which leads to the production of a DsrC-trisulfide. A membrane-bound complex, DsrMKJOP, is present in most organisms that have DsrAB and DsrC, and its involvement in energy conservation has been inferred from sequence analysis, but its precise function was so far not determined. Here, we present studies revealing that the DsrMKJOP complex of the sulfate reducer Archaeoglobus fulgidus works as a menadiol:DsrC-trisulfide oxidoreductase. Our results reveal a close interaction between the DsrC-trisulfide and the DsrMKJOP complex and show that electrons from the quinone pool reduce consecutively the DsrM hemes b, the DsrK noncubane [4Fe-4S]3+/2+ catalytic center, and finally the DsrC-trisulfide with concomitant release of sulfide. These results clarify the role of this widespread respiratory membrane complex and support the suggestion that DsrMKJOP contributes to energy conservation upon reduction of the DsrC-trisulfide in the last step of DSR.

Two-Fold Interpenetrated Binuclear Nickel Metal-Organic Framework as a Heterogeneous Catalyst for N-Heterocycle Synthesis

A binuclear Ni(II)-based metal-organic framework {[Ni2(btb)1.333(H2O)3.578(py)1.422]·(DMF)(H2O)3.25}n (Nibtb) was solvothermally synthesized (H3btb = 1,3,5-tri(4-carboxylphenyl)benzene, py = pyridine, DMF = N,N-dimethylformamide). Nibtb shows a rare 2-fold interpenetrating (3,4)-connected 3D network with a point symbol of (83)4(86)3 based on binuclear Ni(II) clusters. Nibtb as a heterogeneous catalyst combines the high stability of MOFs and excellent catalytic activity of nickel, which exhibits excellent catalytic activity for the synthesis of benzimidazoles and pyrazoles under mild conditions. Moreover, the catalyst can be easily separated and reused for seven successive cycles and maintains high catalytic activity.