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A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs) and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the organic ligand and the inorganic unit. The synthesis and growth of different types of MOFs on substrates with different functionalization, like COOH, OH and pyridine terminated surfaces, were studied and characterized with different surface characterization techniques. A controlled and highly oriented growth of very homogenous films was obtained using this method. The layer-by-layer method offered also the possibility to study the kinetics of film formation in more detail using surface plasmon resonance and quartz crystal microbalance. In addition, this method demonstrates the potential to synthesize new classes of MOFs not accessible by conventional methods. Finally, the controlled growth of MOF thin films is important for many applications like chemical sensors, membranes and related electrodes.

Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal–organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO2 and H2S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures.

To use natural gas as a feedstock alternative to coal and oil, its main constituent, methane, needs to be isolated with high purity 1 . In particular, nitrogen dilutes the heating value of natural gas and is, therefore, of prime importance for removal 2 . However, the inertness of nitrogen and its similarities to methane in terms of kinetic size, polarizability and boiling point pose particular challenges for the development of energy-efficient nitrogen-removing processes 3 . Here we report a mixed-linker metal–organic framework (MOF) membrane based on fumarate ( fum ) and mesaconate ( mes ) linkers, Zr- fum 67 - mes 33 - fcu -MOF, with a pore aperture shape specific for effective nitrogen removal from natural gas. The deliberate introduction of asymmetry in the parent trefoil-shaped pore aperture induces a shape irregularity, blocking the transport of tetrahedral methane while allowing linear nitrogen to permeate. Zr- fum 67 - mes 33 - fcu -MOF membranes exhibit record-high nitrogen/methane selectivity and nitrogen permeance under practical pressures up to 50 bar, removing both carbon dioxide and nitrogen from natural gas. Techno-economic analysis shows that our membranes offer the potential to reduce methane purification costs by about 66% for nitrogen rejection and about 73% for simultaneous removal of carbon dioxide and nitrogen, relative to cryogenic distillation and amine-based carbon dioxide capture. A metal–organic framework membrane based on fumarate and mesaconate linkers is shown to have a pore aperture shape that enables efficient and cost-effective removal of nitrogen and carbon dioxide from methane.

Direct air capture is regarded as a plausible alternate approach that, if economically practical, can mitigate the increasing carbon dioxide emissions associated with two of the main carbon polluting sources, namely stationary power plants and transportation. Here we show that metal-organic framework crystal chemistry permits the construction of an isostructural metal-organic framework ( SIFSIX -3-Cu) based on pyrazine/copper(II) two-dimensional periodic 4 4 square grids pillared by silicon hexafluoride anions and thus allows further contraction of the pore system to 3.5 versus 3.84 Å for the parent zinc(II) derivative. This enhances the adsorption energetics and subsequently displays carbon dioxide uptake and selectivity at very low partial pressures relevant to air capture and trace carbon dioxide removal. The resultant SIFSIX- 3-Cu exhibits uniformly distributed adsorption energetics and offers enhanced carbon dioxide physical adsorption properties, uptake and selectivity in highly diluted gas streams, a performance, to the best of our knowledge, unachievable with other classes of porous materials. The capture and removal of low-concentration carbon dioxide from air is appealing. Here, the authors report a metal-organic framework with a precisely tuned network of pores and optimal charge density, which is capable of carbon dioxide uptake at very low partial pressures relevant to direct air capture.

The electrocatalytic carbon dioxide reduction reaction (CO₂RR) addresses the need for storage of renewable energy in valuable carbon-based fuels and feedstocks, yet challenges remain in the improvement of electrosynthesis pathways for highly selective hydrocarbon production. To improve catalysis further, it is of increasing interest to lever synergies between heterogeneous and homogeneous approaches. Organic molecules or metal complexes adjacent to heterogeneous active sites provide additional binding interactions that may tune the stability of intermediates, improving catalytic performance by increasing Faradaic efficiency (product selectivity), as well as decreasing overpotential. We offer a forward-looking perspective on molecularly enhanced heterogeneous catalysis for CO₂RR. We discuss four categories of molecularly enhanced strategies: molecular-additive-modified heterogeneous catalysts, immobilized organometallic complex catalysts, reticular catalysts and metal-free polymer catalysts. We introduce present-day challenges in molecular strategies and describe a vision for CO₂RR electrocatalysis towards multi-carbon products. These strategies provide potential avenues to address the challenges of catalyst activity, selectivity and stability in the further development of CO₂RR.

Membrane-based approaches can offer energy-efficient and cost-effective methods for various separation processes. Practical membranes must have high permselectivity at industrially relevant high pressures and under aggressive conditions, and be manufacturable in a scalable and robust fashion. We report a versatile electrochemical directed-assembly strategy to fabricate polycrystalline metal–organic framework membranes for separation of hydrocarbons. We fabricate a series of face-centred cubic metal–organic framework membranes based on 12-connected rare-earth or zirconium hexanuclear clusters with distinct ligands. In particular, the resultant fumarate-based membranes containing contracted triangular apertures as sole entrances to the pore system enable molecular-sieving separation of propylene/propane and butane/isobutane mixtures. Prominently, increasing the feed pressure to the industrially practical value of 7 atm promoted a desired enhancement in both the total flux and separation selectivity. Process design analysis demonstrates that, for propylene/propane separation, the deployment of such face-centred cubic Zr-fumarate-based metal–organic framework membranes in a hybrid membrane–distillation system offers the potential to decrease the energy input by nearly 90% relative to a conventional single distillation process. Metal–organic framework membranes may be able to separate mixtures of hydrocarbons in an energy-efficient manner, but high-quality robust membranes are difficult to prepare. Here, Zhou et al. fabricate high-performance continuous metal–organic framework membranes using an electrochemical method.

Metal–organic frameworks have drawn attention as potential catalysts owing to their unique tunable surface chemistry and accessibility. However, their application in thermal catalysis has been limited because of their instability under harsh temperatures and pressures, such as the hydrogenation of CO 2 to methanol. Herein, we use a controlled two-step method to synthesize finely dispersed Cu on a zeolitic imidazolate framework-8 (ZIF-8). This catalyst suffers a series of transformations during the CO 2 hydrogenation to methanol, leading to ~14 nm Cu nanoparticles encapsulated on the Zn-based MOF that are highly active (2-fold higher methanol productivity than the commercial Cu–Zn–Al catalyst), very selective (>90%), and remarkably stable for over 150 h. In situ spectroscopy, density functional theory calculations, and kinetic results reveal the preferential adsorption sites, the preferential reaction pathways, and the reverse water gas shift reaction suppression over this catalyst. The developed material is robust, easy to synthesize, and active for CO 2 utilization. Here, authors report an inter-site structural heterogeneity induced effect of hierarchical single atom Fe catalysts for robust oxygen reduction. Dynamic evolutions and insights into structure-activity relationship are presented.

A prototypical metal-organic framework (MOF), a 2D periodic porous structure based on the assembly of copper ions and benzene dicarboxylate (bdc) ligands (Cu(bdc)·xH2O), was grown successfully as a thin film on interdigitated electrodes (IDEs). IDEs have been used for achieving planar CMOS-compatible low-cost capacitive sensing structures for the detection of humidity and volatile organic compounds (VOCs). Accordingly, the resultant IDEs coated with the Cu(bdc)·xH2O thin film was evaluated, for the first time, as a capacitive sensor for gas sensing applications. A fully automated setup, using LabVIEW interfaces to experiment conduction and data acquisition, was developed in order to measure the associated gas sensing performance.

Gas membrane-based separation is considered one of the most effective technologies to address energy efficiency and large footprint challenges. Various classes of advanced materials, including polymers, zeolites, porous carbons, and metal–organic frameworks (MOFs) have been investigated as potential suitable candidates for gas membrane-based separations. MOFs possess a uniquely tunable nature in which the pore size and environment can be controlled by connecting metal ions (or metal ion clusters) with organic linkers of various functionalities. This unique characteristic makes them attractive for the fabrication of thin membranes, as both the diffusion and solubility components of permeability can be altered. Numerous studies have been published on the synthesis and applications of MOFs, as well as the fabrication of MOF-based thin films. However, few studies have addressed their gas separation properties for potential applications in membrane-based separation technologies. Here, we present a synopsis of the different types of MOF-based membranes that have been fabricated over the past decade. In this review, we start with a short introduction touching on the gas separation membrane technology. We also shed light on the various techniques developed for the fabrication of MOF as membranes, and the key challenges that still need to be tackled before MOF-based membranes can successfully be used in gas separation and implemented in an industrial setting.

Metal–organic frameworks are highly porous materials that are promising for drug release and gas storage. A liquid-phase-epitaxy approach that prevents interpenetration and retains the pore size is now proposed. Metal–organic frameworks (MOFs) are highly porous materials generally consisting of two building elements: inorganic coupling units and organic linkers 1 , 2 , 3 , 4 . These frameworks offer an enormous porosity, which can be used to store large amounts of gases and, as demonstrated in more recent applications 5 , 6 , makes these compounds suitable for drug release. The huge sizes of the pores inside MOFs, however, also give rise to a fundamental complication, namely the formation of sublattices occupying the same space. This interpenetration greatly reduces the pore size and thus the available space within the MOF structure 7 . We demonstrate here that the formation of the second, interpenetrated framework can be suppressed by using liquid-phase epitaxy on an organic template. This success demonstrates the potential of the step-by-step method to synthesize new classes of MOFs not accessible by conventional solvothermal methods.