3D printed MOF-based mixed matrix thin-film composite membranes

MOF-based mixed-matrix membranes (MMMs) have attracted considerable attention due to their tremendous separation performance and facile processability. In large-scale applications such as CO₂ separation from flue gas, it is necessary to have high gas permeance, which can be achieved using thin membranes. However, there are only a handful of MOF MMMs that are fabricated in the form of thin-film composite (TFC) membranes. We propose herein the fabrication of robust thin-film composite mixed-matrix membranes (TFC MMMs) using a three dimensional (3D) printing technique with a thickness of 2-3 μm. We systematically studied the effect of casting concentration and number of electrospray cycles on membrane thickness and CO₂ separation performance. Using a low concentration of polymer of intrinsic microporosity (PIM-1) or PIM-1/HKUST-1 solution (0.1 wt%) leads to TFC membranes with a thickness of less than 500 nm, but the fabricated membranes showed poor CO₂/N₂ selectivity, which could be attributed to microscopic defects. To avoid these microscale defects, we increased the concentration of the casting solution to 0.5 wt% resulting in TFC MMMs with a thickness of 2-3 μm which showed three times higher CO₂ permeance than the neat PIM-1 membrane. These membranes represent the first examples of 3D printed TFC MMMs using the electrospray printing technique.

Thermolabile Cross-Linkers for Templating Precise Multicomponent Metal-Organic Framework Pores

While a number of approaches toward multicomponent metal-organic frameworks have been reported, new strategies affording greater structural versatility and molecular precision are needed to replicate the sophisticated active sites found in enzymes. Here, we outline a general method for templating functional groups within framework pores using thermolabile ligand cross-linkers. We show that tertiary ester-based cross-linkers can be used to install well-defined carboxylic acid pairs at precise relative distances and orientations. The tertiary ester linkages remain intact during framework formation but are readily cleaved to reveal free carboxylic acids upon microwave heating. Successful cross-linker synthesis, framework incorporation, and thermolysis is demonstrated using the mesoporous, terphenyl expanded analogues of MOF-74. When short cross-linkers are used, modeling studies show that the carboxylic acids are installed in a single configuration down the pore channels, spaced ∼7 Å apart. These precisely positioned acid pairs can be used as synthetic handles to build up more complex cooperative active sites.

Linker Engineering toward Full-Color Emission of UiO-68 Type Metal-Organic Frameworks

Luminescent metal-organic frameworks (LMOFs) demonstrate strong potential for a broad range of applications due to their tunable compositions and structures. However, the methodical control of the LMOF emission properties remains a great challenge. Herein, we show that linker engineering is a powerful method for systematically tuning the emission behavior of UiO-68 type metal-organic frameworks (MOFs) to achieve full-color emission, using 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids as luminescent linkers. To address the fluorescence self-quenching issue caused by densely packed linkers in some of the resultant UiO-68 type MOF structures, we apply a mixed-linker strategy by introducing nonfluorescent linkers to diminish the self-quenching effect. Steady-state and time-resolved photoluminescence (PL) experiments reveal that aggregation-caused quenching can indeed be effectively reduced as a result of decreasing the concentration of emissive linkers, thereby leading to significantly enhanced quantum yield and increased lifetime.

Predicting hydrogen storage in MOFs via machine learning

The H2 capacities of a diverse set of 918,734 metal-organic frameworks (MOFs) sourced from 19 databases is predicted via machine learning (ML). Using only 7 structural features as input, ML identifies 8,282 MOFs with the potential to exceed the capacities of state-of-the-art materials. The identified MOFs are predominantly hypothetical compounds having low densities (<0.31 g cm-3) in combination with high surface areas (>5,300 m2 g-1), void fractions (∼0.90), and pore volumes (>3.3 cm3 g-1). The relative importance of the input features are characterized, and dependencies on the ML algorithm and training set size are quantified. The most important features for predicting H2 uptake are pore volume (for gravimetric capacity) and void fraction (for volumetric capacity). The ML models are available on the web, allowing for rapid and accurate predictions of the hydrogen capacities of MOFs from limited structural data; the simplest models require only a single crystallographic feature.

Hydrogen-Bonded Organic Framework Microlasers with Conformation-Induced Color-Tunable Output

Porous organic frameworks have emerged as the promising platforms to construct tunable microlasers. Most of these microlasers are achieved from metal-organic frameworks via meticulously accommodating the laser dyes with the sacrifice of the pore space, yet they often suffer from the obstacles of either relatively limited gain concentration or sophisticated fabrication techniques. Herein, we reported on the first hydrogen-bonded organic framework (HOF) microlasers with color-tunable performance based on conformation-dependent stimulated emissions. Two types of HOF microcrystals with the same gain lumnogen as the building block were synthesized via a temperature-controlled self-assembly method. The distinct frameworks offer different conformations of the gain building block, which lead to great impacts on their conjugation degrees and excited-state processes, resulting in remarkably distinct emission colors (blue and green). Accordingly, blue/green-color lasing actions were achieved in these two types of HOFs based on well-faceted assembled wire-like cavities. These results offer a deep insight on the exploitation of HOF-based miniaturized lasers with desired nanophotonics performances.

Highly Efficient Removal of Neonicotinoid Insecticides by Thioether-Based (Multivariate) Metal-Organic Frameworks

Circumventing the impact of agrochemicals on aquatic environments has become a necessity for health and ecological reasons. Herein, we report the use of a family of five eco-friendly water-stable isoreticular metal-organic frameworks (MOFs), prepared from amino acids, as adsorbents for the removal of neonicotinoid insecticides (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) from water. Among them, the three MOFs containing thioether-based residues show remarkable removal efficiency. In particular, the novel multivariate MOF {Sr^IICu^II₆[(S,S)-methox]_1.5[(S,S)-Mecysmox]_1.50(OH)₂(H₂O)}·36H₂O (5), featuring narrow functional channels decorated with both -CH₂SCH₃ and -CH₂CH₂SCH₃ thioalkyl chains-from l-methionine and l-methylcysteine amino acid-derived ligands, respectively-stands out and exhibits the higher removal efficiency, being capable to capture 100% of acetamiprid and thiacloprid in a single capture step under dynamic solid-phase extraction conditions-less than 30 s. Such unusual combination of outstanding efficiency, high stability in environmental conditions, and low-cost straightforward synthesis in 5 places this material among the most attractive adsorbents reported for the removal of this type of contaminants.

Supramolecular Alloys from Fluorinated Hybrid Tri4 Di6 Imine Cages

To create innovative materials, efficient control and engineering of pore sizes and their characteristics, crystallinity and stability is required. Eight hybrid Tri4 Di6 imine cages with a tunable degree of fluorination and one fully fluorinated Tri4 Di6 imine cage are investigated. Although the fluorinated and the non-fluorinated building blocks used herein differ vastly in reactivity, it was possible to gain control over the outcome of the self-assembly process, by carefully controlling the feed ratio. This represents the first hybrid material based on fluorinated/hydrogenated porous organic cages (POCs). These cages with unlimited miscibility in the solid state were obtained as highly crystalline samples after recrystallization and even showed retention of the crystal lattice, forming alloys. All mixtures and the fully fluorinated Tri4 Di6 imine cage were analyzed by MALDI-MS, single-crystal XRD, powder XRD and in regard to thermal stability (TGA).

Single molecule fluorescence imaging of nanoconfinement in porous materials

This review covers recent progress in using single molecule fluorescence microscopy imaging to understand the nanoconfinement in porous materials. The single molecule approach unveils the static and dynamic heterogeneities from seemingly equal molecules by removing the ensemble averaging effect. Physicochemical processes including mass transport, surface adsorption/desorption, and chemical conversions within the confined space inside porous materials have been studied at nanometer spatial resolution, at the single nanopore level, with millisecond temporal resolution, and under real chemical reaction conditions. Understanding these physicochemical processes provides the ability to quantitatively measure the inhomogeneities of nanoconfinement effects from the confining properties, including morphologies, spatial arrangement, and trapping domains. Prospects and limitations of current single molecule imaging studies on nanoconfinement are also discussed.

What Lies beneath a Metal-Organic Framework Crystal Structure? New Design Principles from Unexpected Behaviors

The rational design principles established for metal-organic frameworks (MOFs) allow clear structure-property relationships, fueling expansive growth for energy storage and conversion, catalysis, and beyond. However, these design principles are based on the assumption of compositional and structural rigidity, as measured crystallographically. Such idealization of MOF structures overlooks subtle chemical aspects that can lead to departures from structure-based chemical intuition. In this Perspective, we identify unexpected behavior of MOFs through literature examples. Based on this analysis, we conclude that departures from ideality are not uncommon. Whereas linker topology and metal coordination geometry are useful starting points for understanding MOF properties, we anticipate that deviations from the idealized crystal representation will be necessary to explain important and unexpected behaviors. Although this realization reinforces the notion that MOFs are highly complex materials, it should also stimulate a broader reexamination of the literature to identify corollaries to existing design rules and reveal new structure-property relationships.

Two-Dimensional Covalent Organic Framework Solid Solutions

Covalent organic frameworks (COFs) generally leverage one or two monomers with specific sizes and shapes to access highly symmetric and periodic polymer networks. Almost all reported COFs employ the minimum sets of monomers needed for the polymerization (usually two, sometimes one) and crystallize in high-symmetry topologies. COFs synthesized from more than two monomers usually employ mixtures with different pendant functionalities to distribute these groups statistically throughout the structure, or monomers with different sizes in ratios targeting lower symmetry topologies. Here, we demonstrate that mixtures of monomers with different lengths generate single-phase, hexagonal two-dimensional covalent organic framework (2D COF) solid solutions at continuously variable feed ratios. X-ray diffraction measurements, Fourier-transform infrared spectroscopy, and Pawley refinement indicate that both monomers distribute randomly within the same lattice, and the lattice parameters continuously increase as more of the larger linker is incorporated. Furthermore, COF solid solutions are accessed directly by polymerizing a mixture of monomers but not via linker exchange from a preformed COF. As strain develops from the lattice accommodating monomers with different sizes, the nonlinear relationship between the monomer incorporation and the COF's lattice parameters suggests that bond-bending of the monomers plays a role in incorporating monomers of different lengths into the solid solutions. Solid solution formation represents a new strategy to design 2D COFs and increase their complexity. Specifically, varying the monomer composition of a given network enables many properties, such as the average pore size, to be continuously tuned between those of corresponding pure COFs.

Continuous Fluidic Techniques for the Precise Synthesis of Metal-Organic Frameworks

The continuous fluidics-based synthesis of metal-organic frameworks (MOFs) has attracted considerable attention, resulting in advancements in the reaction efficiency, a continuous production of complex structures, and access to products that are difficult or impossible to attain by bulk synthetic routes. This Minireview discusses the continuous fluidics-based synthesis of MOFs in terms of reaction process control, and is divided into three chapters dealing with the efficient synthesis of high-quality MOFs, the confined-space synthesis of MOF composites with diverse morphologies, and the selective synthesis of metastable products. The products of continuous fluidic synthetic process are introduced (e. g., uniform products, composites, fibers, membranes, and metastable products with advantageous properties that cannot be obtained by bulk synthesis), and their usefulness is demonstrated by referencing representative examples.

Effective Encapsulation of C60 by Metal-Organic Frameworks with Polyamide Macrocyclic Linkers

A flexible benzylic amide macrocycle, functionalized with two carboxylic acid groups, was employed as the organic ligand for the preparation of robust copper(II)- and zinc(II)-based metal-organic frameworks. These polymers crystallized in the C2/m space group of the monoclinic crystal system, creating non-interpenetrated channels in one direction with an extraordinary solvent-accessible volume of 46 %. Unlike metal-organic rotaxane frameworks having benzylic amide macrocycles as linkers, the absence of the thread in these novel reticular materials causes a decrease of dimensionality and an improvement of pore size and dynamic guest adaptability. We studied the incorporation of fullerene C₆₀ inside the adjustable pocket generated between two macrocycles connected to the same dinuclear clusters, occupying a remarkable 98 % of the cavities inside the network. The use of these materials as hosts for the selective recognition of different fullerenes was evaluated, mainly encapsulating the smaller size fullerene derivative in several mixtures of C₆₀ and C₇₀ .

Regulating metal-organic frameworks as stationary phases and absorbents for analytical separations

Metal-organic frameworks (MOFs) are highly ordered framework systems composed of metal centers and organic linkers formed through coordination bonds. The diversity of metal elements and easily modified organic ligands, together with controllable synthetic approaches, gives rise to the designability of various MOF structures and topologies and the capability of MOFs to be functionalized. Their structural diversity provides MOFs with many unique properties, such as permanent porosity, flexible structures, thermostability, and high adsorption capacity, leading to great practicability in technical applications. In this review, we concentrate on the applications of MOFs in the field of gas chromatography, high-performance liquid chromatography, and the enrichment of biomolecules, based on rational arrangements in the structures and functions of MOFs. Moreover, we emphasize the importance of structural and chemical regulations for the improvement of separation efficiency.

Selective Styrene Oxidation to Benzaldehyde over Recently Developed Heterogeneous Catalysts

The selective oxidation of styrene under heterogeneous catalyzed conditions delivers environmentally friendly paths for the production of benzaldehyde, an important intermediate for the synthesis of several products. The present review explores heterogeneous catalysts for styrene oxidation using a variety of metal catalysts over the last decade. The use of several classes of supports is discussed, including metal-organic frameworks, zeolites, carbon materials and silicas, among others. The studied catalytic systems propose as most used oxidants tert-butyl hydroperoxide, and hydrogen peroxide and mild reaction conditions. The reaction mechanism proceeds through the generation of an intermediate reactive metal-oxygen species by catalyst-oxidant interactions. Overall, most of the studies highlight the synergetic effects among the metal and support for the activity and selectivity enhancement.

Copper mixed-triazolate frameworks featuring the thiophene-containing ligand towards enhanced photodegradation of organic contaminants in water

By using a thiophene-containing triazole ligand -3,5-di(thiophen-2-yl)-1H-1,2,4-triazole (3,5-Th₂-tzH) and 3,5-diphenyl-1H-1,2,4-triazole (3,5-Ph₂-tzH) in different molar ratio in the reactant, copper(I) mixed-triazolate frameworks CuMtz-1 {[Cu₈(3,5-Ph₂-tz)_6-x(3,5-Th₂-tz)_x](BF₄)₂(CH₃OH)₃} (x = 0.5 for CuMtz-1a and 1.1 for CuMtz-1b) were firstly synthesized and characterized by PXRD, IR, ¹H NMR, SEM, TG and UV-vis DRS. They have been evaluated as photocatalysts for the degradation of organic pollutants in water. It was found that the rate constants towards the degradation of both traditional and emerging organic contaminants over CuMtz-1b were significantly improved, i.e. by 160% for methyl orange, 210% for rhodamine B, 80% for methyl blue and 180% for sulfasalazine in comparison with that catalyzed over the parent MOF CuTz-1 {[Cu₈(3,5-Ph₂-tz)₆](BF₄)₂(CH₃OH)₃} under Xe lamp irradiation in the absence of H₂O₂. More importantly, the degradation efficiency of methyl orange and sulfasalazine by CuMtz-1b without the addition of H₂O₂ was quite comparable with that by CuTz-1 with the addition of H₂O₂ under both Xe lamp irradiation and natural sunlight. The enhancement on the degradation efficiency can be attributed to the increased light absorption ability and the change of the band structure caused by the incorporation of thiophene-containing triazole ligand.

Dual Intrareticular Oxidation of Mixed-Ligand Metal-Organic Frameworks for Stepwise Electrochemiluminescence

This work presents a mixed-ligand metal-organic framework (m-MOF) integrated with two ligands, one as a luminophore and the other as a coreactant, on one metal node for self-enhanced electrochemiluminescence (ECL). Both 9,10-di(p-carboxyphenyl)anthracene (DPA) and 1,4-diazabicyclo[2.2.2]octane (D-H₂) ligands can be oxidized, generating the cation radicals DPA^+• and D-H₂^+•, respectively. The latter can be deprotonated to form the neutral radical (D-H^•) and then react with DPA^+• to produce excited DPA* for ECL emission without exogenous coreactants. As a result of the incorporation into the MOF framework and the intrareticular charge transfer between the two ligands, the ECL intensity of the m-MOF was increased 26.5-fold compared with that of the mixture of DPA and D-H₂ in aqueous solution. Moreover, with the process of second oxidation of D-H₂, stepwise ECL emission was observed as a result of local excitation in the DPA unit, which was identified through density functional theory calculations. Overall, the implementation of the mixed-ligand approach, which combines the luminophore and coreactant as linkers in reticular materials, enriches the fundamentals and applications of ECL systems.

In-situ synthesis of uranyl-imprinted nanocage for selective uranium recovery from seawater

Adaptive coordination structure is vital for selective uranium extraction from seawater. By strategy of molecular imprinting, uranyl is introduced into the  m ultivariate metal-organic framework (MOF) during the synthesis process to guide the  in-situ  construction of proper nanocage structure for targeting uranyl binding. Except for  the  coordination between uranium with four oxygen from the materials, the axial oxygen of uranyl also forms hydrogen bonds with hydrogen from the phenolic hydroxyl group, which enhances the binding affinity of the material to uranyl. Attributing to the high binding affinity, the adsorbent shows high uranium binding selectivity to uranyl against not only the interfering metal ions, but also the carbonate group that coordinates with uranyl to form [UO 2 (CO) 3 ] 4 -  in seawater. In natural seawater, the adsorbent realizes a high uranium adsorption capacity of 7.35 mg g -1 , t ogether with an 18.38 times higher selectivity to vanadium.  Integrated into account the high reusability, this adsorbent is a promising alternative for uranium recovery from seawater.

Controlled Shape Evolution of Pure-MOF 1D Microcrystals towards Efficient Waveguide and Laser Applications

MOF-based one-dimensional materials have received increasing attention in the nanophotonics field, but it is still difficult in the flexible shape evolution of MOF micro/nanocrystals for desired optical functionalities due to the susceptible solvothermal growth process. Herein, we report on the well-controlled shape evolution of pure-MOF microcrystals with optical waveguide and lasing performances based on a bottom-up and top-down synergistic method. The MOF microcrystals from solvothermal synthesis (bottom-up) enable the evolution from microrods via microtubes to nanowires through a chelating agent-assisted etching process (top-down). The three types of MOF 1D-microstructures with high crystallinity and smooth surfaces all exhibit efficient optical waveguide performance. Furthermore, MOF nanowire with lowest propagation loss served as low-threshold pure-MOF nanolasers with Fabry-Pérot resonance. These results advance the fundamental understanding on the controlled MOF evolution mechanism, and offer a valuable route for the development of pure-MOF-based photonic components with desired functionalities.

Topological-Distortion-Driven Amorphous Spherical Metal-Organic Frameworks for High-Quality Single-Mode Microlasers

Metal-organic frameworks (MOFs) have recently emerged as appealing platforms to construct microlasers owing to their compelling characters combining the excellent stability of inorganic materials and processable characters of organic materials. However, MOF microstructures developed thus far are generally composed of multiple edge boundaries due to their crystalline nature, which consequently raises significant scattering losses that are detrimental to lasing performance. In this work, we propose a strategy to overcome the above drawback by designing spherically shaped MOFs microcavities. Such spherical MOF microstructures are constructed by amorphizing MOFs with a topological distortion network through introducing flexible building blocks into the growth environment. With an ultra-smooth surface and excellent circular boundaries, the acquired spherical microcavities possess a Q factor as high as ≈10⁴ and can provide sufficient feedback for high-quality single-mode lasing oscillations. We hope that these results will pave an avenue for the construction of new types of flexible MOF-based photonic components.

Single-step synthesis and interface tuning of core-shell metal-organic framework nanoparticles

Control over the spatial distribution of components in metal–organic frameworks has potential to unlock improved performance and new behaviour in separations, sensing and catalysis. We report an unprecedented single-step synthesis of multi-component metal–organic framework (MOF) nanoparticles based on the canonical ZIF-8 (Zn) system and its Cd analogue, which form with a core–shell structure whose internal interface can be systematically tuned. We use scanning transmission electron microscopy, X-ray energy dispersive spectroscopy and a new composition gradient model to fit high-resolution X-ray diffraction data to show how core–shell composition and interface characteristics are intricately controlled by synthesis temperature and reaction composition. Particle formation is investigated by in situ X-ray diffraction, which reveals that the spatial distribution of components evolves with time and is determined by the interplay of phase stability, crystallisation kinetics and diffusion. This work opens up new possibilities for the control and characterisation of functionality, component distribution and interfaces in MOF-based materials.

Core–shell metal–organic framework nanoparticles have been synthesised in which the internal interface and distribution of components is found to be highly tunable using simple variations in reaction conditions.

Effect of Linker Distribution in the Photocatalytic Activity of Multivariate Mesoporous Crystals

The use of Metal-Organic Frameworks as crystalline matrices for the synthesis of multiple component or multivariate solids by the combination of different linkers into a single material has emerged as a versatile route to tailor the properties of single-component phases or even access new functions. This approach is particularly relevant for Zr₆-MOFs due to the synthetic flexibility of this inorganic node. However, the majority of materials are isolated as polycrystalline solids, which are not ideal to decipher the spatial arrangement of parent and exchanged linkers for the formation of homogeneous structures or heterogeneous domains across the solid. Here we use high-throughput methodologies to optimize the synthesis of single crystals of UiO-68 and UiO-68-TZDC, a photoactive analogue based on a tetrazine dicarboxylic derivative. The analysis of the single linker phases reveals the necessity of combining both linkers to produce multivariate frameworks that combine efficient light sensitization, chemical stability, and porosity, all relevant to photocatalysis. We use solvent-assisted linker exchange reactions to produce a family of UiO-68-TZDC_% binary frameworks, which respect the integrity and morphology of the original crystals. Our results suggest that the concentration of TZDC in solution and the reaction time control the distribution of this linker in the sibling crystals for a uniform mixture or the formation of core-shell domains. We also demonstrate how the possibility of generating an asymmetric distribution of both linkers has a negligible effect on the electronic structure and optical band gap of the solids but controls their performance for drastic changes in the photocatalytic activity toward proton or methyl viologen reduction.

Supramolecular cancer nanotheranostics

Among the many challenges in medicine, the treatment and cure of cancer remains an outstanding goal given the complexity and diversity of the disease. Nanotheranostics, the integration of therapy and diagnosis in nanoformulations, is the next generation of personalized medicine to meet the challenges in precise cancer diagnosis, rational management and effective therapy, aiming to significantly increase the survival rate and improve the life quality of cancer patients. Different from most conventional platforms with unsatisfactory theranostic capabilities, supramolecular cancer nanotheranostics have unparalleled advantages in early-stage diagnosis and personal therapy, showing promising potential in clinical translations and applications. In this review, we summarize the progress of supramolecular cancer nanotheranostics and provide guidance for designing new targeted supramolecular theranostic agents. Based on extensive state-of-the-art research, our review will provide the existing and new researchers a foundation from which to advance supramolecular cancer nanotheranostics and promote translationally clinical applications.

Critical Aspects of Metal-Organic Framework-Based Materials for Solar-Driven CO2 Reduction into Valuable Fuels

Photoreduction of CO2 into value-added fuels is one of the most promising strategies for tackling the energy crisis and mitigating the "greenhouse effect." Recently, metal-organic frameworks (MOFs) have been widely investigated in the field of CO2 photoreduction owing to their high CO2 uptake and adjustable functional groups. The fundamental factors and state-of-the-art advancements in MOFs for photocatalytic CO2 reduction are summarized from the critical perspectives of light absorption, carrier dynamics, adsorption/activation, and reaction on the surface of photocatalysts, which are the three main critical aspects for CO2 photoreduction and determine the overall photocatalytic efficiency. In view of the merits of porous materials, recent progress of three other types of porous materials are also briefly summarized, namely zeolite-based, covalent-organic frameworks based (COFs-based), and porous semiconductor or organic polymer based photocatalysts. The remarkable performance of these porous materials for solar-driven CO2 reduction systems is highlighted. Finally, challenges and opportunities of porous materials for photocatalytic CO2 reduction are presented, aiming to provide a new viewpoint for improving the overall photocatalytic CO2 reduction efficiency with porous materials.

Novel Systems and Membrane Technologies for Carbon Capture

Due to the global menace caused by carbon emissions from environmental, anthropogenic, and industrial processes, it has become expedient to consider the use of systems, with high trapping potentials for these carbon-based compounds. Several prior studies have considered the use of amines, activated carbon, and other solid adsorbents. Advances in carbon capture research have led to the use of ionic liquids, enzyme-based systems, microbial filters, membranes, and metal-organic frameworks in capturing CO2. Therefore, it is common knowledge that some of these systems have their lapses, which then informs the need to prioritize and optimize their synthetic routes for optimum efficiency. Some authors have also argued about the need to consider the use of hybrid systems, which offer several characteristics that in turn give synergistic effects/properties that are better compared to those of the individual components that make up the composites. For instance, some membranes are hydrophobic in nature, which makes them unsuitable for carbon capture operations; hence, it is necessary to consider modifying properties such as thermal stability, chemical stability, permeability, nature of the raw/starting material, thickness, durability, and surface area which can enhance the performance of these systems. In this review, previous and recent advances in carbon capture systems and sequestration technologies are discussed, while some recommendations and future prospects in innovative technologies are also highlighted.

Photoresponsive porous materials

Molecular machines, switches, and motors enable control over nanoscale molecular motion with unprecedented precision in artificial systems. Integration of these compounds into robust material scaffolds, in particular nanostructured solids, is a fabrication strategy for smart materials with unique properties that can be controlled with external stimuli. Here, we describe a subclass of these structures, namely light-responsive porous materials metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and porous aromatic frameworks (PAFs) appended with molecular photoswitches. In this review, we provide an overview of a broad range of light-responsive porous materials focusing on potential applications.

Reverse osmosis and nanofiltration membranes for highly efficient PFASs removal: overview, challenges and future perspectives

PFASs are called “forever chemicals” because they do not fully degrade. They have become so ubiquitous in the environment that it is difficult to prevent exposure. This review aims to provide a set of improved technologies to remove PFASs from water.

A new series of 3D lanthanide phenoxycarboxylates: synthesis, crystal structure, magnetism and photoluminescence studies

A new series of 3D Ln-carboxylates was synthesized, where the Tb one shows antiferromagnetic coupling and the Dy one shows ferromagnetic interaction, and with emission spectra combining the intra-4f emission of the Ln ions and that of the ligand.

Structural flexibility in crystalline coordination polymers: a journey along the underlying free energy landscape

In this perspective, we discuss structural flexibility in crystalline coordination polymers. We identify that the underlying free energy landscape unites scientific disciplines, and discuss key areas to advanced the field.

Solvent-assisted delamination of layered copper dithienothiophene-dicarboxylate (DUT-134)

Rational selection of the delamination solvent enables efficient exfoliation of layered MOF, resulting in suspension of the nanosheets stable over days.

Correlated disorder in metal–organic frameworks

Metal–organic frameworks host many types of compositional and structural disorder. In this Highlight article we explore cases where this disorder is correlated, rather than random.

Hammett Relationship in Oxidase-Mimicking Metal-Organic Frameworks Revealed through a Protein-Engineering-Inspired Strategy

While the unique physicochemical properties of nanomaterials that enable regulation of nanozyme activities are demonstrated in many systems, quantitative relationships between the nanomaterials structure and their enzymatic activities remain poorly understood, due to the heterogeneity of compositions and active sites in these nanomaterials. Here, inspired by metalloenzymes with well-defined metal-ligand coordination, a set of substituted metal-organic frameworks (MOFs) with similar coordination is employed to investigate the relationship between structure and oxidase-mimicking activity. Both experimental results and density functional theory calculations reveal a Hammett-type structure-activity linear free energy relationship (H-SALR) of MIL-53(Fe) (MIL = Materials of Institute Lavoisier) nanozymes, in which increasing the Hammett σm value with electron-withdrawing ligands increases the oxidase-mimicking activity. As a result, MIL-53(Fe) NO2 with the strongest electron-withdrawing NO2 substituent shows a tenfold higher activity than the unsubstituted MIL-53(Fe). Furthermore, the generality of H-SALR is demonstrated for a range of substrates, one other metal (Cr), and even one other MOF type (MIL-101). Such biologically inspired quantitative studies demonstrate that it is possible to identify quantitative structure-activity relationships of nanozymes, and to provide detailed insight into the catalytic mechanisms as those in native enzymes, making it possible to use these relationships to develop high-performance nanomaterials.