Wenjia Wu

Hydrogen-bonded organic frameworks (HOFs) have recently emerged as attractive candidates for solid-state electrolytes (SSEs) due to their structurally ordered pores, tunable chemical structures, and solution processability. However, direct application of HOFs as SSEs is challenging because of the lack of mobile Li⁺ and low-energy-barrier transport pathways. Herein, we design and fabricate a HOF-lithium salt array SSE with efficient Li⁺ transport property through integrating lithium salts (Li-salts) into the hydrogen bond networks of HOF nanosheets as conducting sites. Li-salt anions with different electronegativities (TFSI⁻, BF₄⁻, and PF₆⁻) are utilized to investigate their influence on transport environment and Li⁺ conductivity. We demonstrate that the strong hydrogen bond interactions between anions and HOF nanosheets provide a loose coordination environment for Li⁺, enabling efficient Li⁺ transport. Superior ionic conductivity of 1.0 × 10⁻⁴ S cm⁻¹ at 30 °C and high t_Li+ (0.63) are achieved for the optimized SSE. Consequently, the assembled Li|HOF-LiTFSI|Li cell can stably cycle for over 1000 hours at 0.5 mAh cm⁻². The LFP|HOF-LiTFSI|Li half-cell exhibits a satisfactory discharge specific capacity of 161.1 mAh g⁻¹ with a high capacity retention of 99.0% after 300 cycles at 0.5C and 25 °C. This work highlights the great potential of flexible HOFs as high-performance solid-state electrolyte materials.

Hydrogen peroxide (H₂O₂) is widely used in semiconductor cleaning and etching, where ultralow levels of metallic, anionic, organic, and particulate impurities must be strictly controlled. Industrially produced H₂O₂ therefore requires extensive downstream purification before it can meet electronic-grade specifications. Conventional purification routes based on distillation or rectification, adsorption, ion exchange, and final filtration are technically mature, but they remain constrained by substantial energy consumption, multiple treatment stages, chemical regeneration, secondary waste generation, and safety risks associated with H₂O₂ decomposition. This review critically evaluates membrane technologies for purifying and concentrating electronic-grade H₂O₂. Microfiltration and ultrafiltration are discussed as front-end clarification processes, nanofiltration as an intermediate impurity-load-reduction step, and reverse osmosis as the membrane process with the strongest direct experimental for ionic-impurity removal from concentrated H₂O₂. Pervaporation and membrane distillation are assessed as emerging water-removal technologies, although their industrial applicability remains insufficiently validated. Membrane material strategies, including oxidation-resistant polymers, inorganic and hybrid membranes, antioxidant-containing composites, and emerging MOF- and two-dimensional-material-based membranes, are also evaluated. Particular attention is paid to the limited direct evidence available for emerging materials and to the risks of H₂O₂ decomposition, material leaching, particle release, and deterioration of membrane selectivity. The available evidence indicates that membrane processes are currently more appropriately regarded as complementary clarification, purification, polishing, or concentration units rather than complete replacements for established industrial technologies. Future studies should prioritize long-term oxidative stability, ppb- and ppt-level impurity validation, low H₂O₂ loss, module-material compatibility, process safety, and continuous pilot-scale techno-economic assessment.

The electro-oxidation of formaldehyde at low potential with anodic hydrogen evolution offers an energy-saving way for hydrogen production. Coupling this reaction in an acidic catholyte with an alkaline anolyte within an acid-alkali hybrid electrochemical system enables self-powered hydrogen production with electricity generation. However, the performance of such systems is constrained by the membrane: conventional forward-bias bipolar membranes suffer from high ohmic resistance due to the delamination, while monopolar ion exchange membranes lead to undesirable acid-alkali neutralization. To address these limitations, we design a composite ion exchange membrane, composed of a through-pore anion exchange membrane and a cation exchange membrane. Employing this membrane, the resulting system achieves a Faradaic efficiency for hydrogen of 198 ± 3 % and outputs a peak power density of 142 mW cm^-2. A numerical model demonstrates that the through-pore anion exchange membrane effectively regulates charge carrier transport, yielding low resistance and improved acid-alkali utilization efficiency. Here, we provide a promising pathway for sustainable hydrogen production by enabling the efficient conversion of acid-alkali chemical energy into electricity.

Precisely defining proton transport channels and regulating the chemical microenvironment of proton carriers are critical for high-performance proton exchange membranes (PEMs). Beyond optimizing carrier type and density, modulation of electron density distribution offers an underexplored route to enhance intrinsic proton conductivity. Herein, a series of ZnM-BDC-COOH nanosheets are synthesized by partial substitution of Zn²⁺ with a second metal ion in Zn-BDC frameworks and subsequent -COOH modification. The optimized ZnCu-BDC-COOH achieves a high intrinsic proton conductivity of 361.5 mS cm^-1 over 16 times that of the pristine Zn-BDC (22.2 mS cm^-1) at 80 °C and 98% RH using comb electrodes. Density functional theory and molecular dynamics simulations reveal that the introduced Cu²⁺, with higher electronegativity, withdraws more electrons from adjacent -COOH groups and Zn ions, generating asymmetric electron cloud distribution within the O-H bonds and the heterogeneous Zn₃CuO(COO)₆ nodes. This electron asymmetry facilitates rapid H⁺ release and establishes a strong local potential gradient that lowers the proton transport barrier. The resulting ZnCu-BDC-COOH lamellar membrane achieves a peak power density of 0.92 W cm^-2, outperforming Nafion-117 (0.28 W cm^-2), and maintains good durability over 100 h of open-circuit voltage (OCV) under 80 °C and 100% RH in fuel cells.

Two-dimensional metal-organic frameworks (2D MOFs), coupling the individual advantages of organic polymer with excellent flexibility and processability, as well as inorganic crystal with well-ordered and temperature-independent structure, are emerging solid-state electrolyte (SSE) materials for wide-temperature solid-state lithium batteries. However, present MOFs have seldom been directly utilized as SSEs, due to the insurmountable transport energy barrier and resultant low ionic conductivity. Here, we report a lamellar MOF electrolyte with high ionic conductivity over wide-temperature ranges through confining DMF (N, N-dimethylformamide, DMF) solvent into the ordered pore channel of 2D MOF lamellar framework. We demonstrate that, the fine-tuned microstructure of pore walls could induce the rearrangement of DMF solvent layer, forming long-range ordered and stable solvent layer along pore walls. The solvent layer then acts as low-energy-barrier lithium ion transport path, affording MOF SSE high ionic conductivity over wide-temperature ranges (2.87 × 10⁻⁴ – 1.58 × 10⁻³ S cm⁻¹ at −20 – 100 ^oC), surpassing most of the currently reported solid-state electrolytes. The MOF SSE also exhibits high t_Li+ of 0.81 and low activation energy of 0.106 eV. Consequently, the assembled LiFePO₄|Li half-cell can stably cycle over wide-temperature ranges, retaining high discharge specific capacities of 158.4 mAh g⁻¹ at −20 ^oC and 171.2 mAh g⁻¹ at 60 ^oC, respectively, after 300 cycles. This work offers an innovative approach for the design of advanced ion conductors towards wide-temperature solid-state lithium batteries.

Precisely constructing the well‐defined proton transport platform and studying its transport behavior are of great importance yet remain challenging. Here, a Zr‐BTB‐X nanosheet via post‐synthetic modifying Zr‐BTB with terephthalic acid (BDC) and trimesic acid (BTC) is developed, which coordinate to the unsaturated Zr₆ clusters. The increased –COOH groups endow Zr‐BTB‐BTC nanosheets significant improvement in proton conductivity, achieving 490.9 mS cm ⁻¹ at 80 °C and 100% RH, compared to 2.19 mS cm ⁻¹ for the original Zr‐BTB nanosheets. Density functional theory calculations and water adsorption studies reveal that the formation of enriched water networks induced by the –COOH groups facilitates efficient proton dissociation and reduces the proton transport barrier. The assembled Zr‐BTB‐BTC lamellar membrane, retaining high conductivity properties of nanosheet, reaches 242.4 mS cm ⁻¹ at 80 °C and 100% RH. It also delivers a superior performance in proton exchange membrane fuel cell (PEMFC), achieving ultrahigh peak power (0.91 W cm ⁻² ), maximum current density (3.59 A cm ⁻² ), and good durability (100 h of OCV test).

Ionic liquids (ILs) hold great promise as high-performance electrolyte material due to their unique advantages including nonvolatility, high thermal stability, and high ionic conductivity. However, the IL-based electrolytes always suffer from serious ion aggregation and high viscosity at low temperatures, leading to significantly decline in ionic conductivity. Here, hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte (HT-HOF-IL CQSE) was prepared through confining the IL electrolytes (ILEs) into the pore of HOF lamellar framework. The weak hydrogen bonding interactions within HOF nanosheets, together with the generated interactions between ILE and HOF, enable uniform and continuous distribution of ILE in HOF lamellar framework. This effectively inhibits the ion migration of ILE, which meanwhile serves as Li⁺ transfer sites, affording high ionic conductivity of 5.7 × 10^-5 S cm^-1 at -60 ^oC, with high lithium-ion transference number of 0.69, whereas ILEs usually lose ionic conduction ability at such low temperatures. The assembled Li symmetrical cell can stably cycle at 0.2 mA cm^-2 and -20 ^oC for more than 1500 hours. The LiFePO₄|HT-HOF-IL CQSE|Li cell shows excellent cycling performance at 0.5C at a wide temperature range of -20 to 60 ^oC. This work may pave a new avenue for the development of high-performance IL-based composite electrolytes.