ZnO Nanorod-Induced Heteroepitaxial Growth of SOD Type Co-Based Zeolitic Imidazolate Framework Membranes for H2 Separation

Streamlined synthesis of superstructure Ni-benzimidazole MOFs: Glucose electrochemical analysis

The design and synthesis of efficient electrochemical sensors are crucial transformation technologies in electrochemistry. We successfully synthesize a three-dimensional Ni-metal-organic framework (MOF) nanostructured material with a superior architecture using benzimidazole and nickel nitrate as precursors at room temperature which is being applied in glucose electrochemical sensors. The reaction mechanism of M-6 during glucose detection is thoroughly studied using various characterization techniques, such as in situ Raman spectroscopy, in situ ultraviolet-visible spectrophotometry, synchrotron radiography, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The research findings demonstrate that the M-6 material exhibits high sensitivity for glucose detection, with a sensitivity of 2199.88 mA M-1 cm-2. This study provides an important reference for designing more efficient electrochemical reaction systems and optimizing material performance. Furthermore, the superstructural design offers new ideas and possibilities for the development and application of similar materials.

Heat-driven molecule gatekeepers in MOF membrane for record-high H2 selectivity

Hydrogen/carbon dioxide (H₂/CO₂) separation for sustainable energy is in desperate need of reliable membranes at high temperatures. Molecular sieve membranes take their nanopores to differentiate sizes between H₂ and CO₂ but have compromised at a marked loss of selectivity at high temperatures owing to diffusion activation of CO₂. We used molecule gatekeepers that were locked in the cavities of the metal-organic framework membrane to meet this challenge. Ab initio calculations and in situ characterizations demonstrate that the molecule gatekeepers make a notable move at high temperatures to dynamically reshape the sieving apertures as being extremely tight for CO₂ and restitute with cool conditions. The H₂/CO₂ selectivity was improved by an order of magnitude at 513 kelvin (K) relative to that at the ambient temperature.

Robust ultrathin nanoporous MOF membrane with intra-crystalline defects for fast water transport

Rational design of high-performance stable metal–organic framework (MOF) membranes is challenging, especially for the sustainable treatment of hypersaline waters to address critical global environmental issues. Herein, a molecular-level intra-crystalline defect strategy combined with a selective layer thinning protocol is proposed to fabricate robust ultrathin missing-linker UiO-66 (ML-UiO-66) membrane to enable fast water permeation. Besides almost complete salt rejection, high and stable water flux is achieved even under long-term pervaporation operation in hash environments, which effectively addresses challenging stability issues. Then, detailed structural characterizations are employed to identify the type, chemical functionality, and density of intra-crystalline missing-linker defects. Moreover, molecular dynamics simulations shed light on the positive atomistic role of these defects, which are responsible for substantially enhancing structural hydrophilicity and enlarging pore window, consequently allowing ultra-fast water transport via a lower-energy-barrier pathway across three-dimensional sub-nanochannels during pervaporation. Unlike common unfavorable defect effects, the present positive intra-crystalline defect engineering concept at the molecular level is expected to pave a promising way toward not only rational design of next-generation MOF membranes with enhanced permeation performance, but additional water treatment applications.

The development of highly water-permeable membranes is key for the treatment of high salinity waters. Here the authors enhance the water permeability of a metal-organic framework nanoporous membrane via an intra-crystalline defect engineering strategy.

Seed assisted synthesis of anionic metal organic framework membrane for selective and permeable hydrogen separation

Hydrogen selective metal organic framework (MOF) membranes with excellent performances are still in high demand. Here, we are developing an anionic MOF material of CPM-5 into a membrane for H2...

Direct Chemical Vapor Deposition Synthesis of Porous Single-Layer Graphene Membranes with High Gas Permeances and Selectivities

Single-layer graphene containing molecular-sized in-plane pores is regarded as a promising membrane material for high-performance gas separations due to its atomic thickness and low gas transport resistance. However, typical etching-based pore generation methods cannot decouple pore nucleation and pore growth, resulting in a trade-off between high areal pore density and high selectivity. In contrast, intrinsic pores in graphene formed during chemical vapor deposition are not created by etching. Therefore, intrinsically porous graphene can exhibit high pore density while maintaining its gas selectivity. In this work, the density of intrinsic graphene pores is systematically controlled for the first time, while appropriate pore sizes for gas sieving are precisely maintained. As a result, single-layer graphene membranes with the highest H₂ /CH₄ separation performances recorded to date (H₂ permeance > 4000 GPU and H₂ /CH₄ selectivity > 2000) are fabricated by manipulating growth temperature, precursor concentration, and non-covalent decoration of the graphene surface. Moreover, it is identified that nanoscale molecular fouling of the graphene surface during gas separation where graphene pores are partially blocked by hydrocarbon contaminants under experimental conditions, controls both selectivity and temperature dependent permeance. Overall, the direct synthesis of porous single-layer graphene exploits its tremendous potential as high-performance gas-sieving membranes.

Strategies for Improving the Sensing Performance of Semiconductor Gas Sensors for High-Performance Formaldehyde Detection: A Review

Formaldehyde is a poisonous and harmful gas, which is ubiquitous in our daily life. Long-term exposure to formaldehyde harms human body functions; therefore, it is urgent to fabricate sensors for the real-time monitoring of formaldehyde concentrations. Metal oxide semiconductor (MOS) gas sensors is favored by researchers as a result of their low cost, simple operation and portability. In this paper, the mechanism of formaldehyde detection by gas sensors is introduced, and then the ways of ameliorating the response of gas sensors for formaldehyde detection in recent years are summarized. These methods include the control of the microstructure and morphology of sensing materials, the doping modification of matrix materials, the development of new semiconductor sensing materials, the outfield control strategy and the construction of the filter membrane. These five methods will provide a good prerequisite for the preparation of better performing formaldehyde gas sensors.

Sacrificial ZnO nanorods drive N and O dual-doped carbon towards trifunctional electrocatalysts for Zn–air batteries and self-powered water splitting devices

Integrated energy systems (IES) have attracted increasing attention in recent years.

Microporous framework membranes for precise molecule/ion separations

Microporous framework membranes such as metal-organic framework (MOF) membranes and covalent organic framework (COF) membranes are constructed by the controlled growth of small building blocks with large porosity and permanent well-defined micropore structures, which can overcome the ubiquitous tradeoff between membrane permeability and selectivity; they hold great promise for the enormous challenging separations in energy and environment fields. Therefore, microporous framework membranes are endowed with great expectations as next-generation membranes, and have evolved into a booming research field. Numerous novel membrane materials, versatile manipulation strategies of membrane structures, and fascinating applications have erupted in the last five years. First, this review summarizes and categorizes the microporous framework membranes with pore sizes lower than 2 nm based on their chemistry: inorganic microporous framework membranes, organic-inorganic microporous framework membranes, and organic microporous framework membranes, where the chemistry, fabrications, and differences among these membranes have been highlighted. Special attention is paid to the membrane structures and their corresponding modifications, including pore architecture, intercrystalline grain boundary, as well as their diverse control strategies. Then, the separation mechanisms of membranes are covered, such as diffusion-selectivity separation, adsorption-selectivity separation, and synergetic adsorption-diffusion-selectivity separation. Meanwhile, intricate membrane design to realize synergistic separation and some emerging mechanisms are highlighted. Finally, the applications of microporous framework membranes for precise gas separation, liquid molecule separation, and ion sieving are summarized. The remaining challenges and future perspectives in this field are discussed. This timely review may provide genuine guidance on the manipulation of membrane structures and inspire creative designs of novel membranes, promoting the sustainable development and steadily increasing prosperity of this field.

H2/CO2 separations in multicomponent metal-adeninate MOFs with multiple chemically distinct pore environments

Metal-organic frameworks constructed from multiple (≥3) components often exhibit dramatically increased structural complexity compared to their 2 component (1 metal, 1 linker) counterparts, such as multiple chemically unique pore environments and a plurality of diverse molecular diffusion pathways. This inherent complexity can be advantageous for gas separation applications. Here, we report two isoreticular multicomponent MOFs, bMOF-200 (4 components; Cu, Zn, adeninate, pyrazolate) and bMOF-201 (3 components; Zn, adeninate, pyrazolate). We describe their structures, which contain 3 unique interconnected pore environments, and we use Kohn-Sham density functional theory (DFT) along with the climbing image nudged elastic band (CI-NEB) method to predict potential H₂/CO₂ separation ability of bMOF-200. We examine the H₂/CO₂ separation performance using both column breakthrough and membrane permeation studies. bMOF-200 membranes exhibit a H₂/CO₂ separation factor of 7.9. The pore space of bMOF-201 is significantly different than bMOF-200, and one molecular diffusion pathway is occluded by coordinating charge-balancing formate and acetate anions. A consequence of this structural difference is reduced permeability to both H₂ and CO₂ and a significantly improved H₂/CO₂ separation factor of 22.2 compared to bMOF-200, which makes bMOF-201 membranes competitive with some of the best performing MOF membranes in terms of H₂/CO₂ separations.

Halloysite nanotubes (HNTs)@ZIF-67 composites—a new type of heterogeneous catalyst for the Knoevenagel condensation reaction

Halloysite nanotubes (HNTs) are encapsulated in 50 nm thick shells of ZIF-67, producing novel nano-sized composites HNTs@ZIF-67.

Zeolite Imidazolate Framework Membranes on Polymeric Substrates Modified with Poly(vinyl alcohol) and Alginate Composite Hydrogels

Poly(vinyl alcohol)-sodium alginate composite hydrogels were first introduced to synthesize robust and well-intergrown zeolite imidazolate framework (ZIF)/polymer hollow fiber membranes. Through enough adsorption interaction with metal ions by chelation, sufficient nucleation sites for in situ metal-organic framework (MOF) preparation are provided. Using this method, we can not only easily prepare defect-free MOF membranes ignoring the complex modification process and seed deposition but also structurally fix crystalline MOF layers and greatly improve the stiffness and durability of MOF composite membranes. The strategy also gives the appropriate level of generality for synthesis of versatile dense MOF membranes on a variety of polymeric supports. The fabricated ZIF-8/polyethersulfone membrane presented remarkable gas separation performance with H₂ permeance of as high as 9.66 × 10^-7 mol m^-2 s^-1 Pa^-1 and a high H₂/CO₂ separation factor of up to 29.0.

Etching gas-sieving nanopores in single-layer graphene with an angstrom precision for high-performance gas mixture separation

One of the bottlenecks in realizing the potential of atom-thick graphene membrane for gas sieving is the difficulty in incorporating nanopores in an otherwise impermeable graphene lattice, with an angstrom precision at a high-enough pore density. We realize this design by developing a synergistic, partially decoupled defect nucleation and pore expansion strategy using O₂ plasma and O₃ treatment. A high density (ca. 2.1 × 10¹² cm^-2) of H₂-sieving pores was achieved while limiting the percentage of CH₄-permeating pores to 13 to 22 parts per million. As a result, a record-high gas mixture separation performance was achieved (H₂ permeance, 1340 to 6045 gas permeation units; H₂/CH₄ separation factor, 15.6 to 25.1; H₂/C₃H₈ separation factor, 38.0 to 57.8). This highly scalable pore etching strategy will accelerate the development of single-layer graphene-based energy-efficient membranes.