A scalable metal-organic framework as a durable physisorbent for carbon dioxide capture

Calcium Alginate Aerogel-MIL160 Nanocomposites for CO2 Removal

Using MOFs in powder form leads to mass transfer limitations and large pressure drops in packed bed adsorbers. Use of MOF/aerogel composites (called MOFACs) in bead form could overcome these challenges without compromising the MOF's adsorption performance, as observed with other shaping methods, such as the use of polymeric binders. In this study, Ca-alginate-aerogel-MIL-160(Al) MOFACs (AlgMIL160) were prepared via sol/gel-assisted direct mixing methods, followed by supercritical drying. The gas sorption, powder X-ray diffraction, FTIR, and scanning electron microscopy characterization results showed that the MOF was successfully incorporated into the aerogel, while the MOF structure was preserved. Adsorption measurements were carried out in both static single-component and dynamic binary gas mixture modes. Obtained isotherms were successfully fitted to the Langmuir model followed by ideal adsorbed solution theory (IAST). The single-component gas adsorption isotherms of CO2 on MOFACs with MIL-160(Al) loadings of 25, 50, and 75 wt % revealed a CO2 uptake of 0.43, 0.70, and 0.98 mmol/g at 150 mbar and 25 °C which were higher than that of pure MOF (1.23 mmol/g) based on the MOF loading in the composites, showing the synergistic effect of aerogel and MOF composites. Incorporation of MIL-160(Al) into the aerogel network which is comprised of 75% MIL-160(Al) and 25% Ca-alginate aerogel enhanced MIL-160(Al)'s CO2/N2 IAST selectivity from 53 to 70 at 25 °C and 1000 mbar. Both experimental and simulated CO2 adsorption isotherms showed good agreement. The dynamic adsorption performance of the MOFACs studied by using a binary mixture of 15% CO2/85% N2 was close to the single-component CO2 adsorption with slightly decreased uptake showing the competitive adsorptions between CO2 and N2 molecules. This novel nanocomposite with remarkable CO2 capture performance can be used in gas adsorbers without causing large pressure drops.

Recent advances and challenges of metal-organic frameworks for CO2 capture

Carbon dioxide (CO2) emissions resulting from extensive fossil fuel consumption have become an increasingly critical global challenge, underscoring the importance of carbon capture and separation technologies. As emerging porous materials, metal-organic frameworks (MOFs) exhibit remarkable potential for CO2 capture due to their unique structures and tunable properties. Current MOF-based CO2 capture methods have been broadly categorized into two major mechanisms: chemisorption and physisorption. By precisely tailoring MOF pore size and shape, creating unsaturated metal sites, and introducing functional groups, researchers significantly boost CO2 capture efficiency. This Frontier article discussed these two mechanisms and highlighted the latest advances in MOF-based CO2 capture, offering valuable guidelines for the development of novel MOF-related technologies.

In Pursuit of Carbon Neutrality: Progresses and Innovations in Sorbents for Direct Air Capture of CO2

Direct air capture (DAC) is of immense current interest, as a means to facilitate CO2 capture at low concentrations (∼400 ppm) directly from the atmosphere, with the aim of addressing global warming caused by excessive anthropogenic CO2 production. Traditionally, DAC of CO2 has relied on amine scrubbing and metal carbonate /hydroxide solutions. However, recent years have seen notable progress in DAC sorbents, with key advancements aimed at improving efficiency, capacity, and regenerability while reducing energy consumption. This review delivers an exhaustive analysis of contemporary developments in DAC sorbents, addressing the innovations in material design and consequent performance enhancement. The limitations of the sorbents have also been discussed, with future perspectives for improving sustainable CO2 capture strategies. We anticipate that this overview will help lay the groundwork for further development and large-scale implementation of sustainable sorbents and cutting-edge technologies toward attaining carbon neutrality.

Challenges and insights in CO2 adsorption using N-doped carbons under realistic conditions

N-doped carbon was synthesized from an N-rich precursor, chitosan, and systematically compared with materials reported in the literature to evaluate its potential for CO2 capture in post-combustion scenarios and biogas upgrading under realistic conditions. The synthesized material, with 5.2 at.% nitrogen and a high surface area of 1000 m2 g-1, exhibited moderate CO2 uptake (2.6 mmol g-1) and an ideal CO2/N2 selectivity (SCO2/N2) of 20.4 under post-combustion conditions (15% vol. CO2, 1 bar, 298 K). For equimolar CO2/CH4 mixtures (50% vol. CO2), the material showed an ideal CO2/CH4 selectivity (SCO2/CH4) of 3.3 under the same conditions. When exposed to humidity, the material adsorbed CO2 efficiently at low relative humidity (RH) levels, but suffered a significant loss of capacity at 30% RH, attributed to water-induced site blocking. A comparison with other N-doped/enriched materials from the literature revealed difficulties in correlating CO2 adsorption and selectivity with specific material properties, such as surface area and nitrogen content. This underscores the complexity of defining universal design principles for CO2 capture.

Retrospective Review on Reticular Materials: Facts and Figures Over the Last 30 Years

The field of reticular materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), is expanding continuously - be it in terms of novel structures, advanced characterization techniques, or record-breaking physical properties for applications. This timeline review reflects on the progress over the past 30 years, complemented by input from the community of active researchers. Owing to a global, crowdsourced survey of 228 researchers that is conducted through an online questionnaire, recent insights into the demographics of the field are given. Besides revealing how it works, publish, and interact, the review highlights both academic and industrial milestones. The contemporary trends are described, both at the level of material development and their suitability for a range of applications. To pave the way for newcomers to the field, some remaining challenges and steps to overcome them are discussed. The findings from this contemplative review aim to shape the future course of research in this domain.

High Structural Error Rates in "Computation-Ready" MOF Databases Discovered by Checking Metal Oxidation States

"Computation-ready" metal-organic framework (MOF) databases provide essential raw data for high-throughput computational screening (HTS) and machine-learning approaches to materials discovery. However, the structural fidelity of these databases remains largely unquantified. We introduce MOSAEC, an algorithm that detects chemically invalid structures based on metal oxidation states. MOSAEC was manually validated against 14,796 MOF structures from the popular CoRE database and found to flag erroneous structures with 96% accuracy. Examination of 14 leading experimental and hypothetical MOF databases containing >1.9 million structures reveals structural error rates exceeding 40% in most cases. Analysis of 8 recent HTS studies which highlighted top-performing candidates shows that 52% of these structures were chemically invalid.

Reticular Chemistry within Crystalline Porous Gas Adsorbents and Membranes

ConspectusAdsorptive and membrane separations are recognized as highly energy-efficient technologies, critically dependent on the properties of adsorbent and membrane materials. Crystalline porous materials (CPMs), such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), metal-organic cages (MOCs), and hydrogen-bonded organic frameworks (HOFs), have emerged as exceptional candidates for high-performance adsorbents and membranes due to their intrinsic structural tunability. Their orderly pore structure, high porosity, and large surface facilitate gas storage and separation processes. Furthermore, modifying the inner surface, controlling the pore size, and regulating the framework flexibility can significantly enhance CPMs' adsorption capacity and separation selectivity. Therefore, the precise structure regulation of CPMs is the key to optimizing gas separation and purification.Reticular chemistry is the use of strong chemical bonds to connect discrete molecular structures (molecules or molecular clusters) to create extended structures, such as CPMs. It allows precise atomic-level control and offers a method for regulating the structures of CPMs, enabling tailored pore environments that enhance selectivity for target separations. This approach is crucial to designing effective gas separation materials. For example, by functionalizing organic ligands, regulating metal ions, and modifying secondary building units, the pore size, porosity, and functionality of CPMs can be finely controlled while keeping the framework topology unchanged, thereby optimizing the gas separation performance.In this Account, we present an overview of our group's research efforts on optimizing gas separation by fine-tuning CPM adsorbents and membranes. Using reticular chemistry, we have developed strategies such as multiple cooperative regulation, adaptive pore control, pore environment engineering, preprocessed monomer interfacial polymerization, and precursor solution processing to create highly selective CPM adsorbents and membranes. Additionally, we elucidate the underlying mechanism of multiple hydrogen bonding and dipole-dipole interactions between CPMs and hydrocarbon molecules. By precise structural regulation, we further optimize the gas separation performance and broaden CPMs' applications. Finally, we discuss the challenges and future directions for CPM adsorbents and membranes, including material design, synthesis, stability, performance, and the structure-activity relationship. We also propose a membrane-adsorptive separation coupling technology as a potential solution for achieving high-purity gas separation. By utilizing CPM-based adsorbents and membranes, we aim to establish an energy-intensive and environmentally friendly pathway for the separation of low-carbon hydrocarbons, hydrogen, and natural gas, providing a sustainable alternative to conventional high-energy gas separation processes.

Adsorption Equilibrium and Transport of CO2, N2, and H2O in CALF-20

CALF-20 is a hydrophobic MOF adsorbent demonstrated at a pilot scale for the capture of CO2 from wet flue gas using a direct steam heating TSA cycle. It has been synthesized following a published protocol, and its XRD structure matches known results. Both crystals and particles are used to study single-component adsorption and the diffusion of CO2, N2, and H2O by using gravimetric, volumetric, and dynamic column breakthrough methods. Temperature and relative humidity ranges explored are 25-150 °C and 0-95% in helium, respectively, up to 1 bar pressure. A steam-helium mixture is used above 100 °C. Small pressure steps are used to determine (approximately) locally constant transport parameters. The Sips-Henry isotherm is the best-fit model, which correctly captures the dependence of the isosteric heat of adsorption on adsorbent loading, especially the complex shape for H2O. The pore diffusion model captures crystal uptakes. The micropore diffusivity is an increasing function of the adsorbed-phase concentration up to a certain level before showing reversal, which is consistent with the Darken equation, a function of isotherm curvature. Gas/moisture transport in CALF-20 particles is controlled by Knudsen diffusion in the macropores. The key features observed from the single-component adsorption and diffusion studies and their impact on process studies are demonstrated by applying them to predict breakthrough results.

Upgrading Electron Transfer with High Conductivity MOF Composites for Supercapacitors

Supercapacitors (SCs) have emerged as promising energy storage devices, offering flexibility and smart functionalities to meet the growing demands of modern applications. However, challenges such as limited conductivity and stability continue to hinder their performance. Herein, a conductive composite was designed by forming one-dimension rod-like conductive MOFs (Ni-HHTP) on the hierarchical nickel oxalate (Ni-OA). The extended conjugated system between Ni2+ and HHTP establishes a robust electron delocalization network, significantly enhancing the conductivity and stability of the MOFs. Simultaneously, the incorporation of Ni-HHTP with Ni-OA effectively reduces internal electron transfer impedance, improving charge transport within the delocalized electronic networks. The synthesized Ni-OA@Ni-HHTP-6//AC achieves a remarkable energy density of 24.78 Wh kg-1 at a power density of 113.03 W kg-1, with a peak power density of 2924.58 W kg-1 at an energy density of 19.68 Wh kg-1. This work provides valuable insights into the design of oxalate@conductive-MOF composites, paving the way for energy storage devices.

Simultaneous Capture of N2O and CO2 from a N2O/N2/CO2/O2 Mixture with a Ni(II)-Pyrazolecarboxylate Framework

Nitrous oxide (N2O) is a potent greenhouse gas and a major contributor to ozone depletion. Its primary industrial emission source is tail gas from adipic acid production, which typically comprises a mixture of N2O, CO2, N2, and O2. Current technologies for the removal of N2O and CO2 from tail gas are energy-intensive and operationally complex. Herein, for the first time, simultaneous capture of N2O and CO2 from the quaternary mixture is achieved using a Ni(II)-pyrazolecarboxylate framework, BUT-167. This material demonstrated an exceptional adsorption capacity (135.8 cm3 cm-3 at 40 kPa) and a high packing density (790 mg cm-3) for N2O, outperforming reported sorbents. Moreover, BUT-167 also exhibits a remarkable CO2 adsorption capacity (101.5 cm3 cm-3 at 4 kPa), achieving simultaneously high selectivity values of 257.6 for CO2/N2 (4:96, v/v) and 135.7 for N2O/N2 (40/60). Importantly, BUT-167 exhibits robust and outstanding dual-gas removal performance across multiple adsorption-desorption breakthrough cycles under both dry and humid conditions. The strong affinity toward CO2 and N2O could be attributed to multiple hydrogen bonding interactions facilitated by its highly confined channel structure, as confirmed through single-crystal X-ray diffraction analysis.

Understanding Metal-Organic Framework Densification: Solvent Effects and the Growth of Colloidal Primary Nanoparticles in Monolithic ZIF-8

To commercialize metal-organic frameworks (MOFs), it is vital they are made easier to handle. There have been many attempts to synthesize them as pellets, tablets, or granules, though they come with innate drawbacks. Only recently have these been overcome, through the advent of self-shaping densified or monolithic MOFs (monoMOFs), which require minimal post-synthetic modification and avoid poor structural integrity, intractability, and pore collapse or blockage. ZIF-8 (zeolitic imidazolate framework-8) has emerged as a prototypical monoMOF in pure and in situ doped forms. Now its formation in solvent mixtures is studied to better understand the early stages of monolith formation and improve the scope of monoliths for hosting solvent-sensitive guests. Solvent-, temperature- and coagulant-dependent control over reaction kinetics induces variations in morphology that are explained by relating the nucleation and growth rates of primary nanocrystallites to the stability of colloidal dispersions during reaction. This yields mesoporous monoZIF-8 with mean pore size 16 nm, SBET >1400 m2 g-1, bulk density 0.76 g cm-3, and resistance to permanent deformation exceeding previous reports. While the study highlights the powerful manipulation of monoMOF characteristics, a new understanding of the growth and stability of primary nanocrystallites has consequences for colloid synthesis generally.

Sandwiching of MOF nanoparticles between graphene oxide nanosheets among ice grains

Current strategies to tailor the formation of nanoparticle clusters require specificity and directionality built into the surface functionalization of the nanoparticles by involved chemistries that can alter their properties. Here, we describe a non-disruptive approach to place nanomaterials of different shapes between nanosheets, i.e., nano-sandwiches, absent any pre-modification of the components. We demonstrate this with metal-organic frameworks (MOFs) and silicon oxide (SiO2) nanoparticles sandwiched between graphene oxide (GO) nanosheets, MOF-GO and SiO2-GO, respectively. For the MOF-GO, the MOF shows significantly enhanced conductivity and retains its original crystallinity, even after one-year exposure to aqueous acid/base solutions, where the GO effectively encapsulates the MOF, shielding it from polar molecules and ions. The MOF-GOs are shown to effectively capture CO2 from a high-humidity flue gas while fully maintaining their crystallinities and porosities. Similar behavior is found for other MOFs, including water-sensitive HKUST-1 and MOF-5, promoting the use of MOFs in practical applications. The nanoparticle sandwich strategy provides opportunities for materials science in the design of nanoparticle clusters consisting of different materials and shapes with predetermined spatial arrangements.

The structuring of porous reticular materials for energy applications at industrial scales

Reticular synthesis constructs crystalline architectures by linking molecular building blocks with robust bonds. This process gave rise to reticular chemistry and permanently porous solids. Such precise control over pore shape, size and surface chemistry makes reticular materials versatile for gas storage, separation, catalysis, sensing, and healthcare applications. Despite their potential, the transition from laboratory to industrial applications remains largely limited. Among various factors contributing to this translational gap, the challenges associated with their formulation through structuring and densification for industrial compatibility are significant yet underexplored areas. Here, we focus on the shaping strategies for porous reticular materials, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), to facilitate their industrial application. We explore techniques that preserve functionality and ensure durability under rigorous industrial conditions. The discussion highlights various configurations - granules, monoliths, pellets, thin films, gels, foams, and glasses - structured to maintain the materials' intrinsic microscopic properties at a macroscopic level. We examine the foundational theory and principles behind these shapes and structures, employing both in situ and post-synthetic methods. Through case studies, we demonstrate the performance of these materials in real-world settings, offering a structuring blueprint to inform the selection of techniques and shapes for diverse applications. Ultimately, we argue that advancing structuring strategies for porous reticular materials is key to closing the gap between laboratory research and industrial utilization.

Enhance Water Electrolysis for Green Hydrogen Production with Material Engineering: A Review

Water electrolysis, a traditional and highly technology, is gaining significant attention due to the growing demand for renewable energy resources. It stands as a promising solution for energy conversion, offer substantial benefits in environmental protection and sustainable development efforts. The aim of this research is to provide a concise review of the current state-of-the-art in the field of water electrolysis, focusing on the principles of water splitting fundamental, recent advancements in catalytic materials, various advanced characterization methods and emerging electrolysis technology improvements. Moreover, the paper delves into the development trends of catalysts engineering for water electrolysis, providing insight on how to enhance the catalytic performance. With the advancement of technology and the reduction of costs, hydrogen production through water electrolysis is expected to assume a more significant role in future energy ecosystem. This paper not only synthesizes existing knowledge but also highlights emerging opportunities and potential advancements in this field, offering a clear roadmap for further research and innovation.

Selective adsorption of CO2 in TAMOF-1 for the separation of CO2/CH4 gas mixtures

TAMOF-1 is a robust, highly porous metal-organic framework built from Cu2+ centers linked by a L-histidine derivative. Thanks to its high porosity and homochirality, TAMOF-1 has shown interesting molecular recognition properties, being able to resolve racemic mixtures of small organic molecules in gas and liquid phases. Now, we have discovered that TAMOF-1 also offers a competitive performance as solid adsorbent for CO2 physisorption, offering promising CO2 adsorption capacity ( > 3.8 mmol g-1) and CO2/CH4 Ideal Adsorbed Solution Theory (IAST) selectivity ( > 40) at ambient conditions. Moreover, the material exhibits favorable adsorption kinetics under dynamic conditions, demonstrating good stability in high-humidity environments and minimal degradation in strongly acidic media. We have identified the key interactions of CO2 within the TAMOF-1 framework by a combination of structural (neutron diffraction), spectroscopic and theoretical analyses which conclude a dual-site adsorption mechanism with the majority of adsorbed CO2 molecules occupying the empty voids in the TAMOF-1 channels without strong, directional supramolecular interactions. This very weak dominant binding opens the possibility of a low energy regeneration process for convenient CO2 purification. These features identify TAMOF-1 as a viable solid-state adsorbent for the realization of affordable biogas upgrading.

Amine-Functionalized Triazolate-Based Metal-Organic Frameworks for Enhanced Diluted CO2 Capture Performance

Efficient CO2 capture at concentrations between 400-2000 ppm is essential for maintaining air quality in a habitable environment and advancing carbon capture technologies. This study introduces NICS-24 (National Institute of Chemistry Structures No. 24), a Zn-oxalate 3,5-diamino-1,2,4-triazolate framework with two distinct square-shaped channels, designed to enhance CO2 capture at indoor-relevant concentrations. NICS-24 exhibits a CO2 uptake of 0.7 mmol/g at 2 mbar and 25 °C, significantly outperforming the compositionally related Zn-oxalate 1,2,4-triazolate - CALF-20 (0.17 mmol/g). Improved performance is attributed to amino-functions that enhance CO2 binding and enable superior selectivity over N2 and O2, achieving 8-fold and 30-fold improvements, respectively, in simulated CO2/N2 and CO2/O2 atmospheric ratios. In humid environments, NICS-24 retained structural integrity but exhibited an 85 % reduction in CO2 capacity due to competitive water adsorption. Breakthrough sorption experiments, atomistic NMR analysis, and DFT calculations revealed that water preferentially adsorbs over CO2 due to strong hydrogen-bonding interactions within the framework. Gained understanding of the interaction between CO2 and H2O within the MOF framework could guide the modification via rational design with improved performance under real-world conditions.

Uncovering the Dynamic CO2 Gas Uptake Behavior of CALF-20 (Zn) under Varying Conditions via Positronium Lifetime Analysis

Carbon dioxide (CO2) is a major greenhouse gas contributing to global warming. Adsorption in porous sorbents offers a promising method for CO2 capture and storage. The zinc-triazole-oxalate-based Calgary framework 20 (CALF-20) demonstrates high CO2 capacity, low H2O affinity, and low adsorption heat, enabling energy-efficient and stable performance over multiple cycles. This study examines CO2 adsorption mechanism in CALF-20 using positron annihilation lifetime spectroscopy (PALS), in situ powder X-ray diffraction (PXRD), and gas adsorption experiments under varying temperatures and humidity levels. Variable-temperature PALS experiments demonstrate that CO₂ molecules are spatially localized within the CALF-20 cages, leaving temperature- and pressure-dependent gaps. CO2 begins at cage centers, forming 1D chains, and ultimately adheres to pore walls. Interestingly, positronium intensity correlates with the Langmuir-Freundlich isotherm, reflecting gas uptake behavior. Moreover, under pure relative humidity (RH), water molecules form isolated clusters or small oligomers at low RH, transitioning to hydrogen-bonded networks above 35 %RH, significantly altering free volumes. In humid CO₂ conditions, competitive interactions arise: CO₂ initially disrupts water propagation, but higher RH leads to extensive water networks filling the framework. The synergy between in situ-PALS, in situ-PXRD, and gas adsorption techniques provides comprehensive insights into CALF-20's potential for efficient CO2 capture under varying conditions.

Kinetic Separation of Butane Isomers Using a Formate Metal-Organic Framework

n-butane (n-C4H10) and isobutane (i-C4H10) are important raw materials in chemical industry. The separation of the two hydrocarbon isomers via distillation is challenging and energy-consuming. Herein we report the adsorption behavior of a microporous cobalt formate framework [Co3(HCOO)6] for potential kinetic separation of butane isomers. Under ambient condition, [Co3(HCOO)6] shows near adsorption capacity for n-C4H10 (1.77 mmol g-1) and i-C4H10 (1.36 mmol g-1) with different adsorption kinetics. Study on the adsorption kinetics for butane indicates that the smaller isomer is adsorbed at a higher diffusion rate, resulting in a high kinetic selectivity of 193 for n-C4H10/i-C4H10 separation. Analyses of adsorption kinetics and breakthrough experiment have validated the separation potential of [Co3(HCOO)6] for butane purification.

Development of a Multiparticulate Metal-Organic Framework/Textile Fiber Swatch

The versatility of metal-organic frameworks (MOFs) has led to groundbreaking applications in a wide variety of fields, especially in the areas of energy, environment, and sustainability. For example, MOFs can be designed for high uptake of toxic gases and pollutants, such as CO2, NH3, and SO2, but designing a single MOF that shows tangible uptake for all of these gases is challenging due to the differences in the chemical and physical properties of these molecules. To this end, integrating multiple MOFs onto textile fibers and crafting various structures have emerged as pivotal developments, enhancing framework durability and usability. MOF composites prepared on readily available textile fibers offer the flexibility essential for critical applications, including heterogeneous catalysis, chemical sensing, toxic gas adsorption, and drug delivery, while preserving the unique characteristics of MOFs. This study introduces a scalable and adaptable method for seamlessly embedding multiple high-performing MOFs onto a single textile fiber using a dip-coating method. We explored the uptake capacity of these multi-MOF composites for CO2, NH3, and SO2 and observed a performance similar to that of traditional powdered materials. Along with harmful gas adsorption, we also have evaluated the permeation and reactivity of these MOF/textile composites toward chemical warfare agents (CWAs) like GD (soman), HD (mustard gas), and VX. In combination, these results demonstrate a fundamental advancement toward establishing a consistent strategy for the hydrolysis of nerve agents in real-world scenarios. This approach can substantially increase the protection toward CWAs and enhance the effectiveness of protective equipment such as fabrics for protective garments. This dip-coating method for the integration of multiple MOFs on a single textile fiber unlocks a wealth of possibilities and paves the way for future innovations in the deployment of MOF-based composites.

Insight into the Specific Adsorption of Cu(II) by a Zinc-Based Metal-Organic Framework Mediated via a Proton-Exchange Mechanism

In the context of scarce metal resources, the one-step separation and recovery of high-value copper metal ions from secondary resources is of significant importance and presents substantial challenges. This study identified a Zn-based triazole MOF (Zn(tr)(OAc)) with accessible and noncoordinated terminal hydroxyl groups within its framework. The Zn(tr)(OAc) surpasses most currently reported Cu-specific MOF adsorbents regarding adsorption capacity and Cu2+ selectivity. Furthermore, in the one-step separation and recovery experiment of Cu2+, the Cu2+ concentration was increased from 79.64% in the simulated secondary copper resource solution to 98.62% in the adsorbed phase. Both experimental and theoretical studies indicated that the high ion selectivity for Cu2+ is primarily due to the specific recognition ability of the terminal hydroxyl (-OH) group, enabling only Cu2+ to undergo proton exchange with the hydrogen. The strong adsorption capacity of the material was attributed not only to proton exchange between the hydroxyl groups in the framework and Cu2+ but also to interactions between the nitrogen (N) and oxygen (O) atoms in the heterocyclic rings and Cu2+. In summary, Zn(tr)(OAc) demonstrates great potential in the separation and recovery of Cu2+ from secondary copper resources and provides additional possibilities for enhancing Cu2+ selectivity in MOF-based adsorbents.

Surpassing stoichiometric limitation for supra-multi-molar adsorption and separation of acid gases

Capture of acid gases holds crucial importance for addressing air pollution and climate change, where achieving a molar ratio for adsorption and separation of acid gases on an active site higher than 1.0 remains challenging. Herein, we demonstrate that three nitrogen-bonded one Zn sites within a single-crystalline-like porous carbon (Zn-N3@SC-PC) derived from controlled carbonization of ZIF-8-C ≡ N with KCl, exhibit supra-multi-molar adsorption for CO2, COS, and H2S, even to 1:6 ratio for SO2 on the Zn-N3. This exceptional performance is attributed to the protruded structure in the Zn-N3@SC-PC for more coordination between Zn vacant orbital and acid gases evidenced by DFT calculation and in situ EXAFS. The high capacity for capturing acid gases on this adsorbent is crucial for future in carbon neutrality and environment protection.

Understanding the Key Role of Cations in Water Tolerance during the CO2/CO Separation Process under Low-Humidity Conditions

The efficient separation of CO2 and CO under low-humidity conditions is crucial for ensuring the long-term operational stability of industrial applications. While the number of adsorbent cations plays a key role in separation, their influence on purification under low humidity remains insufficiently understood. The breakthrough results indicate that, even under extremely low humidity, the adsorption capacity of CO2 and CO can decrease by up to 6 and 24%, respectively. It is found that the presence of water could increases the CO2/CO separation factor from 6.91 to 9. This enhancement occurs because CO, with its lower quadrupole moment, experiences a more significant reduction in adsorption capacity than CO2. The quantity and accessibility of cations significantly influence the water tolerance in adsorption processrs. As the number of cations decreases, CO adsorption stabilizes due to the associated hydrophobicity. However, for CO2, the high accessibility of cations at the S3 site in NaX(88) facilitates its conversion to stable carbonates and bicarbonates in the presence of water, enabling exceptional water resistance. These findings offer valuable insights into designing high-performance adsorbents for efficient CO2 capture and separation from industrial flue gas under low-humidity conditions.

Ionic porous materials: from synthetic strategies to applications in gas separation and catalysis

Ionic porous materials possess a unique combination of tunable pore sizes and task-specific interactions between guest molecules and the charged frameworks, which endow them with versatility across diverse domains in chemistry and materials science. Significant advancements in their applications for gas separation and catalysis have been achieved in recent years due to the incorporation of ionic functionalities and ultra-microporous structures that enable molecular-scale recognition of guest molecules. This review summarizes recent advancements in the synthetic strategies of ionic porous materials, establishing design guidelines for the incorporation of ionic moieties into the backbone to fine-tune pore sizes and chemistry. It highlights the synergistic interplay of task-specific interactions with custom-designed pore structures in key applications, including adsorption separation, membrane separation, and gas conversion. Additionally, it examines structure-property relationships, offering deeper insights into enhancing performance. The report also addresses the current challenges in the practical application of these materials. Finally, the review provides future perspectives on ionic porous materials from both scientific and industrial viewpoints. Overall, this review aims to provide insights into pore structure and chemistry, supporting the precise placement of ionic functionalities.

Eco-friendly one-pot hydrothermal synthesis of cyclodextrin metal-organic frameworks for enhanced CO2 capture

Polysaccharide-based metal-organic frameworks have attracted widespread attention due to their combination of the biocompatibility and flexibility of polysaccharides. Cyclodextrin are interesting bio-ligands in the construction of polysaccharide-based MOFs. Conventional methods for preparing cyclodextrin metal-organic frameworks (CD-MOFs) are often time-consuming and inefficient. In this study, cost-effective and environmentally friendly α- and β-CD-MOFs were successfully synthesized using a hydrothermal method, with optimized incubation time and solvent ratios. The materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N₂ adsorption/desorption measurements. The CO₂ adsorption mechanism was also examined using Fourier transform infrared spectroscopy (FTIR). The results demonstrated excellent thermal and cycling stability of the materials. The CO₂ uptake capacities of α- and β-CD MOF-K were 10.8 and 11.2 cm3/g, respectively. Additionally, the CD-MOFs showed strong selectivity for CO₂ over N₂. Given the straightforward operational procedures, safety characteristics, and mild reaction conditions of CD-MOFs, it is reasonable to conclude that they are promising candidates for use as CO₂ adsorption materials.

A Hydrolytically Stable Metal-Organic Framework for Simultaneous Desulfurization and Dehydration of Wet Flue Gas

Metal-organic frameworks (MOFs) have great prospects as adsorbents for industrial gas purification, but often suffer from issues of water stability and competitive water adsorption. Herein, we present a hydrolytically stable MOF that could selectively capture and recover trace SO2 from flue gas, and exhibits remarkable recyclability in the breakthrough experiments under wet flue-gas conditions, due to its excellent resistance to the corrosion of SO2 and the water-derived capillary forces. More strikingly, its SO2 capture efficiency is barely influenced by the increasing humidity, even if the pore filling with water is reached. Mechanistic studies demonstrate that the delicate pore structure with diverse pore dimensions and chemistry leads to different adsorption kinetics and thermodynamics as well as segregated adsorption domains of SO2 and H2O. Significantly, this non-competitive adsorption mechanism enables simultaneous desulfurization and dehydration by a single adsorbent, opening an avenue toward cost-effective and simplified processing flowcharts for flue gas purification.

Lanthanide Oxalates: From Single Crystals to 2D Functional Honeycomb Nanosheets

Oxalates are simple, low-cost but crucial compounds in the technology of lanthanides, actinides, and transition metals. Apart from using oxalate as a versatile ligand in coordination chemistry, simple oxalate salts are still under a scientific focus, linked with ion batteries, optical and magnetic materials, and, most importantly, industrial-technological mining and separation loops. The typically low solubility of oxalate salts is advantageous from the viewpoint of a convenient and affordable synthesis requiring only green solvents. Even though basic lanthanide oxalates have been known for decades, their structural descriptions have remained fuzzy, especially concerning water content and heavy lanthanide analogues. Herein, we present a newly developed preparation technique for large oxalate monocrystals applied to the whole lanthanide series. All of the structures were reviewed, and some new structures were determined. All of these oxalates exhibit a honeycomb structure with closed cavities containing water molecules. These honeycomb coordination polymers form a layered structure bonded by hydrogen bonds. Surprisingly, most oxalates can be easily exfoliated/delaminated in EtOH, forming colloids of up to single-layered nanosheets. Such a feature has never been described for 2D lanthanide oxalates and demonstrates a new form of applicability for them, e.g., for the construction of thin films or inkjet-printed layers using an extremely facile and economical preparation route.

17O NMR Spectroscopy Reveals CO2 Speciation and Dynamics in Hydroxide-Based Carbon Capture Materials

Carbon dioxide capture technologies are set to play a vital role in mitigating the current climate crisis. Solid-state 17O NMR spectroscopy can provide key mechanistic insights that are crucial to effective sorbent development. In this work, we present the fundamental aspects and complexities for the study of hydroxide-based CO2 capture systems by 17O NMR. We perform static density functional theory (DFT) NMR calculations to assign peaks for general hydroxide CO2 capture products, finding that 17O NMR can readily distinguish bicarbonate, carbonate and water species. However, in application to CO2 binding in two test case hydroxide-functionalised metal-organic frameworks (MOFs) - MFU-4l and KHCO3-cyclodextrin-MOF, we find that a dynamic treatment is necessary to obtain agreement between computational and experimental spectra. We therefore introduce a workflow that leverages machine-learning force fields to capture dynamics across multiple chemical exchange regimes, providing a significant improvement on static DFT predictions. In MFU-4l, we parameterise a two-component dynamic motion of the bicarbonate motif involving a rapid carbonyl seesaw motion and intermediate hydroxyl proton hopping. For KHCO3-CD-MOF, we combined experimental and modelling approaches to propose a new mixed carbonate-bicarbonate binding mechanism and thus, we open new avenues for the study and modelling of hydroxide-based CO2 capture materials by 17O NMR.

Hydrophobic Metal-Formate Composites for Efficient CO2 Capture

Carbon capture, utilization, and sequestration (CCUS) have emerged as pivotal mitigation strategies in addressing climate change induced by greenhouse gas emissions. In this pursuit, our objective is to enhance the efficacy of adsorptive CO2 capture by harnessing state-of-the-art framework sorbents engineered for exceptional CO2 selectivity, high intrinsic stability in the presence of moisture, and facile regeneration. To this end, a series of ultramicroporous mixed aluminum and iron formate framework materials, Fe-ALFs, were synthesized. Furthermore, their moisture stability has been significantly enhanced by passivation with polyvinylidene fluoride (Fe-ALF-PVDF). Gas sorption and breakthrough measurements demonstrate that Fe-ALF-PVDF exhibits outstanding CO2 adsorption capacities (4.6 mmol/g at 298 K) and remarkable CO2/N2 selectivity (387). In addition, it can be economically produced from readily available chemicals and is easy to regenerate. Fe-ALF-PVDF presents an innovative adsorbent material for efficiently capturing CO2 from humid postcombustion flue gases and other moisture-rich gas streams.

Enhancing CO2 Capture Via Fast Microwave-Assisted Synthesis of the CALF-20 Metal-Organic Framework

Metal-organic frameworks (MOFs) are promising porous materials for CO2 adsorption due to their high surface area, tunable properties, and selective adsorption capabilities. The recently reported Calgary Framework 20 (CALF-20) MOF has very appealing CO2 capture properties: high uptake capacity; low regeneration energy; durability (>450 000 cycles) under steam and wet acid gases; simple and scalable synthesis. This study investigates the microwave (MW)-assisted synthesis of CALF-20, which reduces reaction time 12-fold while enhancing the synthesis yield to 97%. Structural analysis confirmed that MW-synthesized CALF-20 retains its crystallographic structure and shows improved CO2 capture performance, exhibiting higher adsorption capacity (∼20% higher), selectivity, and lower regeneration energy. This method provides a rapid and efficient alternative for producing the CALF-20 adsorbent for CO2 capture and separation applications.

From Fundamentals to Synthesis: Covalent Organic Frameworks as Promising Materials for CO2 Adsorption

Covalent organic frameworks (COFs) are highly crystalline polymers that possess exceptional porosity and surface area, making them a subject of significant research interest. COF materials are synthesized by chemically linking organic molecules in a repetitive arrangement, creating a highly effective porous crystalline structure that adsorbs and retains gases. They are highly effective in removing impurities, such as CO2, because of their desirable characteristics, such as durability, high reactivity, stable porosity, and increased surface area. This study offers a background overview, encompassing a concise discussion of the current issue of excessive carbon emissions, and a synopsis of the materials most frequently used for CO2 collection. This review provides a detailed overview of COF materials, particularly emphasizing their synthesis methods and applications in carbon capture. It presents the latest research findings on COFs synthesized using various covalent bond formation techniques. Moreover, it discusses emerging trends and future prospects in this particular field.

Architecting Metal-Organic Frameworks at Molecular Level toward Direct Air Capture

Escalating carbon dioxide (CO2) emissions have intensified the greenhouse effect, posing a significant long-term threat to environmental sustainability. Direct air capture (DAC) has emerged as a promising approach to achieving a net-zero carbon future, which offers several practical advantages, such as independence from specific CO2 emission sources, economic feasibility, flexible deployment, and minimal risk of CO2 leakage. The design and optimization of DAC sorbents are crucial for accelerating industrial adoption. Metal-organic frameworks (MOFs), with high structural order and tunable pore sizes, present an ideal solution for achieving strong guest-host interactions under trace CO2 conditions. This perspective highlights recent advancements in using MOFs for DAC, examines the molecular-level effects of water vapor on trace CO2 capture, reviews data-driven computational screening methods to develop a molecularly programmable MOF platform for identifying optimal DAC sorbents, and discusses scale-up and cost of MOFs for DAC.

Hexaazatrinaphthylene-Based Ultrastable Metal-Organic Frameworks Modulated by the Chelating Coordination Configuration for CO2 Capture

Hexaazatrinaphthylene (HATN), a polyheterocyclic aromatic ligand, is ideal for constructing discrete functional coordination complexes. However, its conjugated rigidity has resulted in a great challenge in forming extended structures with only one 3D metal-organic framework (MOF) reported 24 years ago. Herein, by regulation of the dihedral angle between two chelating HATN planes, three new porous HATN-based MOFs (SNNU-231-233) with mononuclear metal centers were successfully synthesized. SNNU-231, a unique 2-fold interpenetrated MOF, was first assembled, but the interpenetration leads to the lost pores. By modulating coordination configurations, the pore channels were successfully opened in SNNU-232 and SNNU-233, leading to a new topology in SNNU-232 and breaking the interpenetration in SNNU-233. All HATN-based MOFs exhibit exceptional thermal stability above 500 °C, surpassing most reported MOF materials. At the same time, SNNU-233 can keep its structure in water from pH = 1 to 14. Specifically, SNNU-233 had outstanding CO2 uptake capacity and separation ability of CO2/N2 due to its strong affinity to CO2 molecules in specific pores with abundant hydrogen bonds and π-force adsorption sites. SNNU-233 also showed significant potential for the simulated low calorific value coal gases with five components of H2 (5.1%), CO (9.1%), CH4 (5.0%), N2 (66.3%), and CO2 (14.3%).

Assembling Giant Nanoclusters as Heterogeneous Catalysts for Effectively Converting CO2 to CO Under Visible Light

Heterometallic lanthanide-transition metal (3d-4f) nanoclusters with well-defined structures and multiple active sites are excellent vehicles for achieving efficient catalysis and studying heterometallic synergism. In this work, two closely related yet different high-nuclearity nanoclusters, 72-nuclear {Ni28RE44} (1, RE = Pr, Nd, Sm, Eu, and Gd) and 111-nuclear {Ni48La63} (2), are synthesized using a mixed-ligand strategy. Importantly, the crystal solids of these giant coordination clusters are insoluble when soaking in H2O/CH3CN and can be used as heterogeneous catalysts for visible-light-driven catalytic conversion of CO2 to CO. Cluster 2 exhibits a maximum CO production rate of 4800 µmol g-1 h-1 and a CO selectivity of 92% over H2. Furthermore, the catalytic properties are investigated of different rare earths in the cluster 1 series, found that 1-Eu exhibited superior catalytic performance under identical conditions, likely due to the lower reduction potential of the europium ions. This study represents the first report of 3d-4f heterometallic nanoclusters as heterogeneous catalysts for photocatalytic reaction and provides a reference for the study of high-nuclearity 3d-4f nanoclusters as catalysts for photocatalytic reduction of CO2 to CO.

Combining Brillouin Light Scattering Spectroscopy and Machine-Learned Interatomic Potentials to Probe Mechanical Properties of Metal-Organic Frameworks

The mechanical properties of metal-organic frameworks (MOFs) are of high fundamental and practical relevance. A particularly intriguing technique for determining anisotropic elastic tensors is Brillouin scattering, which so far has rarely been used for highly complex materials like MOFs. In the present contribution, we apply this technique to study a newly synthesized MOF-type material, referred to as GUT2. The experiments are combined with state-of-the-art simulations of elastic properties and phonon bands, which are based on machine-learning force fields and dispersion-corrected density functional theory. This provides a comprehensive understanding of the experimental signals, which can be correlated to the longitudinal and transverse sound velocities of the material. Notably, the combination of the insights from simulations and experiments allows the determination of approximate values for the components of the elastic tensor of the studied material even when dealing with comparably small single crystals, which limit the range of accessible experimental data.

Cost Estimation of the Production of MIL-100(Fe) at Industrial Scale from Two Upscaled Sustainable Synthesis Routes

Understanding the impact of MOF synthesis conditions on the production cost is vital in order to have a competitive product with a view toward industrial applications. Here, considering the benchmark mesoporous iron(III) trimesate MIL-100(Fe) as a prototypical example, we show that the production cost can reach <30 $/kg if a careful selection of the synthetic route is made. Two routes were considered in the analysis, using sulfate and nitrate as iron sources. A new optimized synthesis protocol in a 5 L laboratory pilot-scale reactor based on iron sulfate was developed using optimized sustainable aqueous ambient pressure conditions, leading to larger particles and a higher space-time yield. Based on reliable pilot-scale data and established chemical engineering estimation methods, this leads to a significantly lower production cost of high-quality MIL-100(Fe), achieving a potential competitive product.

Superhydrophobic and Self-Healing Porous Organic Macrocycle Crystals for Methane Purification under Humid Conditions

Purifying methane from natural gas using adsorbents not only requires the adsorbents to possess excellent separation performance but also to overcome additional daunting challenges such as humidity interference and durability requirements for sustainable use. Herein, porous organic crystals of a new macrocycle (CaC9) with superhydrophobic and self-healing features are prepared and employed for the purification of methane (>99.99% purity) from ternary methane/ethane/propane mixtures under 97% relative humidity. The high selectivity for methane and water-resistance are attributed to the unique chemical structure of CaC9, possessing an intrinsic 4.2 Å pore along with a pore environment modified with saturated alkyl chains. Besides, CaC9 crystals exhibit a self-healing capacity to realize in situ reconstruction of porosity within 15 min. The transformation of CaC9 crystals from a nonporous state to a porous state can be easily achieved upon treatment with n-hexane vapor, thereby presenting a novel solution to enhance the sustainable separation processes of porous materials. This work introduces a novel molecular-level porous adsorbent for natural gas separation, providing a valuable impetus for designing novel adsorbents with unexpected functions.

Negative gas adsorption transitions and pressure amplification phenomena in porous frameworks

Nanoporous solids offer a wide range of functionalities for industrial, environmental, and energy applications. However, only a limited number of porous materials are responsive, i.e. the nanopore dynamically alters its size and shape in response to external stimuli such as temperature, pressure, light or the presence of specific molecular stimuli adsorbed inside the voids deforming the framework. Adsorption-induced structural deformation of porous solids can result in unique counterintuitive phenomena. Negative gas adsorption (NGA) is such a phenomenon which describes the spontaneous release of gas from an "overloaded" nanoporous solid via adsorption-induced structural contraction leading to total pressure amplification (PA) in a closed system. Such pressure amplifying materials may open new avenues for pneumatic system engineering, robotics, damping, or micromechanical actuators. In this review we illustrate the discovery of NGA in DUT-49, a mesoporous metal-organic framework (MOF), and the subsequent examination of conditions for its observation leading to a rationalization of the phenomenon. We outline the development of decisive experimental and theoretical methods required to establish the mechanism of NGA and derive key criteria for observing NGA in other porous solids. We demonstrate the application of these design principles in a series of DUT-49-related model compounds of which several also exhibit NGA. Furthermore, we provide an outlook towards applying NGA as a pressure amplification material and discuss possibilities to discover novel NGA materials and other counterintuitive adsorption phenomena in porous solids in the future.

Supramolecular Chemistry in Metal-Organic Framework Materials

Far from being simply rigid, benign architectures, metal-organic frameworks (MOFs) exhibit diverse interactions with their interior environment. From developing crystal sponges to studying reactions in framework materials, the role of both supramolecular chemistry and framework structure is evident. We explore the role of supramolecular chemistry in determining framework…guest interactions and attempts to understand the dynamic behavior in MOFs, including attempts to control pore behavior through the incorporation of mechanically-interlocked molecules. Appreciating and understanding the role of supramolecular interactions and dynamic behavior in metal-organic frameworks emerge as important directions for the field.

Transitioning metal-organic frameworks from the laboratory to market through applied research

Metal-organic frameworks (MOFs) have captivated researchers for over 25 years, yet few have successfully transitioned to commercial markets. This Perspective elucidates the progress, challenges and opportunities in moving MOFs to market, focusing on applied research. The five applied research steps that enable technology development and demonstration are reviewed: synthesis, forming, processing (washing and activation), prototyping and compliance. Furthermore, the importance of a comprehensive techno-economic analysis incorporating a complete picture of costs and revenues is discussed. Readers can use the understanding of applied research presented herein to tackle their MOF commercialization challenges.

Ab Initio Predictions of Adsorption in Flexible Metal-Organic Frameworks for Water Harvesting Applications

Metal-organic frameworks such as MOF-303 and MOF-LA2-1 have demonstrated exceptional performance for water harvesting applications. To enable a reticular design of such materials, an accurate prediction of the adsorption properties with chemical accuracy and fully accounting for the flexibility is crucial. The computational prediction of water adsorption properties in MOFs has become standard practice, but current methods lack the predictive power needed to design new materials. Limitations stem from the way the interatomic potential is described and the inadequate consideration of the framework flexibility. Herein, we showcase a methodology to obtain chemically accurate adsorption isotherms that fully account for framework flexibility. The method relies on very accurate and efficiently trained machine learning potentials and transition matrix Monte Carlo simulations to account for framework flexibility. For MOF-303, quantitatively accurate adsorption isotherms are obtained, provided an accurately benchmarked electronic structure method is used to train the machine learning potential, and local and global framework flexibility is accounted for. The broader applicability is shown through the study of MOF-333 and MOF-LA2-1. Analysis of the water density profiles in the MOFs gives insight into the factors governing the shape and origin of the isotherm. An optimal water harvester should have initial seeding sites with intermediate adsorption strength to prevent detrimental low-pressure water uptake. To increase the working capacity, linker extension strategies can be used while maintaining the initial seeding sites, as was done in MOF-LA2-1. The methodology can be applied to other guest molecules and MOFs, enabling the future design of MOFs with specific adsorption properties.

Nanoconfinement-Driven Energy-Efficient CO2 Capture and Release at High Pressures on a Unique Large-Pore Mesoporous Carbon

Although microporous carbons can perform well for CO2 separations under high pressure conditions, their energy-demanding regeneration may render them a less attractive material option. Here, we developed a large-pore mesoporous carbon with pore sizes centered around 20-30 nm using a templated technical lignin. During the soft-templating process, unique cylindrical supramolecular assemblies form from the copolymer template. This peculiar nanostructuring takes place due to the presence of polyethylene glycol (PEG) segments on both the Pluronic® template and the PEG-grafted lignin derivative (glycol lignin). A large increase in CO2 uptake occurs on the resulting large-pore mesoporous carbon at 270 K close to the saturation pressure (3.2 MPa), owing to capillary condensation. This phenomenon enables a CO2/CH4 selectivity (SCO2/CH4, mol/mol) of 3.7 at 270 K and 3.1 MPa absolute pressure, and a swift pressure swing regeneration process with desorbed CO2 per unit pressure far outperforming a benchmark activated carbon (i.e., notably rapid decrease in the amount of adsorbed CO2 with decreasing pressure). We propose large-pore mesoporous carbons as a novel family of CO2 capture adsorbents, based on the phase-transition behavior shift of CO2 in the nanoconfined environment. This novel material concept may open new horizons for physisorptive CO2 separations with energy-efficient regeneration options.

Adsorption and Separation by Flexible MOFs

Flexible metal-organic frameworks (MOFs) offer unique opportunities due to their dynamic structural adaptability. This review explores the impact of flexibility on gas adsorption, highlighting key concepts for gas storage and separation. Specific examples demonstrate the principal effectiveness of flexible frameworks in enhancing gas uptake and working capacity. Additionally, mixed gas adsorption and separation of mixtures are reviewed, showcasing their potential in selective gas separation. The review also discusses the critical role of the single gas isotherms analysis and adsorption conditions in designing separation experiments. Advanced combined characterization techniques are crucial for understanding the behavior of flexible MOFs, including monitoring of phase transitions, framework-guest and guest-guest interactions. Key challenges in the practical application of flexible adsorbents are addressed, such as the kinetics of switching, volume change, and potential crystal damage during phase transitions. Furthermore, the effects of additives and shaping on flexibility and the "slipping off effect" are discussed. Finally, the benefits of phase transitions beyond improved working capacity and selectivity are outlined, with a particular focus on the advantages of intrinsic thermal management. This review highlights the potential and challenges of using flexible MOFs in gas storage and separation technologies, offering insights for future research and application.

Removal of Trace Benzene from Cyclohexane Using a MOF Molecular Sieve

Cyclohexane (Cy), commonly produced by the catalytic hydrogenation of benzene (Bz), is used in large quantities as a solvent or feedstock for nylon polymers. Removing trace unreacted Bz from the Cy product is technically difficult due to their similar molecular structures and physical properties. Herein, we report that a metal-organic framework (MOF) adsorbent shows a molecular sieving effect for Bz and Cy with record-high Bz/Cy adsorption selectivities (216, 723, and 1027) in their liquid mixtures (v/v = 1:1, 1:10, and 1:20), and traps Bz molecules effectively even at low partial pressure in the vapor phase (e.g., 2.49 mmol/g at 8.2 Pa) or at low content in liquid-phase Cy (e.g., 128 mg/g at 20 ppm). Over 99% removal of trace Bz (1000 ppm) from liquid Cy could be achieved in one simple stripping step at room temperature using this sorbent, producing a Cy with >99.999% purity. Single-crystal structure analyses for guest-free and Bz-loaded phases of the MOF disclosed that a narrow slit-like pore aperture and the strong uniting of multiple weak host-guest and guest-guest interactions are the co-origin of its distinct adsorption property for Bz and Cy.

Beyond Tradition: A MOF-On-MOF Cascade Z-Scheme Heterostructure for Augmented CO2 Photoreduction

Metal-organic frameworks (MOFs) are rigorously investigated as promising candidates for CO2 capture and conversion. MOF-on-MOF heterostructures integrate bolstered charger carrier separation with the intrinsic advantages of MOF components, exhibiting immense potential to substantially escalate the efficiency of photocatalytic CO2 reduction (CO2RR). However, the structural and compositional complexity poses significant challenges to the controllable development of these heterostructures. Herein, a conventional MOF-on-MOF nanocomposite is readily optimized from a type II heterojunction to a state-of-the-art cascade Z-scheme configuration via the encapsulation of Pt nanoparticles (Pt NPs), establishing synergistic MOF-MOF and metal-MOF heterojunctions with reinforced built-in electric field. A cascade electron flow is thus propelled, vigorously separating the photogenerated charge carriers and profoundly extending their lifetimes. Collectively, the photocatalytic activity of the cascade Z-scheme is drastically promoted, exhibiting a nearly quintuple enhancement in the CO production rate over the original type II heterostructure. Moreover, the anti-sintering capacity of the developed nanocomposite is unveiled, elucidating its simultaneously improved activity and stability. These findings present unprecedented regulation over the configuration of a MOF-on-MOF heterojunction, substantially enriching the fundamental understanding and rational design strategies of composite materials.

Metal-Modified Zr-MOFs with AIE Ligands for Boosting CO2 Adsorption and Photoreduction

The design and synthesis of metal-organic frameworks (MOFs) with outstanding light-harvesting and photoexcitation for artificial photocatalytic CO2 reduction is an attractive but challenging task. In this work, a novel aggregation-induced emission (AIE)-active ligand, tetraphenylpyrazine (PTTBPC) is proposed and utilized for the first time to construct a Zr-MOF photocatalyst via coordination with stable Zr-oxo clusters. Zr-MOF is featured by a scu topology with a two-fold interpenetrated framework, wherein the PTTBPC ligands enable strong light-harvesting and photoexcitation, while the Zr-oxo clusters facilitate CO2 adsorption and activation, as well as offer potential sites for further metal modification. Consequently, the Zr-PTTBPC and its Co/Ni derivatives not only exhibit exceptional stability and high CO2 adsorption capability (73 cm3 g-1 at 273 K and 1 atm), but also demonstrate a CO production rate of up to 293.2 µmol g h-1 under 420 nm LED light that can be reused for at least three cycles. With insights from charge-carrier dynamics and theoretical calculations, the underlying mechanism is revealed, confirming that the single-phase multi-component synergy is the key for the outstanding photocatalytic CO2 reduction. This work showcases a brand-new type of MOF photocatalyst based on AIE ligands and their promising applications in photocatalytic C1 conversion.

Green Synthesis of a New Schiff Base Linker and Its Use to Prepare Coordination Polymers

Solid-state synthesis is an approach to organic synthesis that is desirable because it can offer minimal or no solvent waste, high yields, and relatively low energy footprints. Herein, we report the solid-state synthesis of a novel Schiff base, 4-{(E)-[(4-methylpyridin-3-yl)imino]methyl}benzoic acid (4-PIBZ), synthesized through the reaction of an amine and an aldehyde. 4-PIBZ was prepared via solvent-drop (water) grinding (SDG) on a multigram scale with 97% yield and was characterized using FTIR, 1H NMR, and SCXRD. The pyridyl and carboxylate moiety present in 4-PIBZ make it suitable for use as a linker ligand and indeed 4-PIBZ was found to coordinate with Cu(II), Zn(II), and Cd(II) cations, enabling it to serve as a linker ligand for the assembly of coordination polymers. 4-PIBZ thereby formed 1D (spiro chain) and 2D (square lattice, sql, topology) coordination polymers via solvent-induced (layering or slurry) methods. The resulting coordination polymers were characterized though X-ray diffraction (SCXRD, PXRD) and TGA, further demonstrating the utility of green synthesis methods for the preparation of some classes of new linker ligands that can in turn be used for the preparation of coordination polymers.

Integration of ordered porous materials for targeted three-component gas separation

Separation of multi-component mixtures in an energy-efficient manner has important practical impact in chemical industry but is highly challenging. Especially, targeted simultaneous removal of multiple impurities to purify the desired product in one-step separation process is an extremely difficult task. We introduced a pore integration strategy of modularizing ordered pore structures with specific functions for on-demand assembly to deal with complex multi-component separation systems, which are unattainable by each individual pore. As a proof of concept, two ultramicroporous nanocrystals (one for C2H2-selective and the other for CO2-selective) as the shell pores were respectively grown on a C2H6-selective ordered porous material as the core pore. Both of the respective pore-integrated materials show excellent one-step ethylene production performance in dynamic breakthrough separation experiments of C2H2/C2H4/C2H6 and CO2/C2H4/C2H6 gas mixture, and even better than that from traditional tandem-packing processes originated from the optimized mass/heat transfer. Thermodynamic and dynamic simulation results explained that the pre-designed pore modules can perform specific target functions independently in the pore-integrated materials.

The Road Ahead for Metal-Organic Frameworks: Current Landscape, Challenges and Future Prospects

This perspective highlights the transformative potential of Metal-Organic Frameworks (MOFs) in environmental and healthcare sectors. It discusses work that has advanced beyond technology readiness levels of >4 including applications in capture, storage, and conversion of gases to value added products. This work showcases efforts in the most salient applications of MOFs which have been performed at a great cadence, enabled by the federal government, large companies, and startups to commercialize these technologies despite facing significant challenges. This article also forecasts the role of nanoscale MOFs in healthcare, including strides toward personalized medicine, advocating for their use in custom-tailored drug delivery systems. Finally we underscore the potential acceleration in MOF research and development through the integration of machine learning and AI, positioning MOFs as versatile tools poised to address global sustainability and health challenges.

Advances in chemistry of CALF-20, a metal-organic framework for industrial gas applications

The metal-organic framework CALF-20 is a super-stable adsorbent utilised for carbon dioxide capture and storage in cement plants. Furthermore, recent findings suggest its potential for various gas-related applications. In this brief review, we summarise ten years of research on CALF-20, emphasising its historical background and key findings. We discuss its flexibility, stability, processability, and tunability, detailing how these properties contribute to advancements in CALF-20 chemistry. We believe that this information will provide a better understanding of CALF-20 and assist in evaluating the potential of both novel and existing materials for gas-related applications.