CO2 adsorption under humid conditions: Self-regulated water content in CAU-10

MFM-300(Sc): a chemically stable Sc(III)-based MOF material for multiple applications

Developing robust multifunctional metal-organic frameworks (MOFs) is the key to advancing the further deployment of MOFs into relevant applications. Since the first report of MFM-300(Sc) (MFM = Manchester Framework Material, formerly known as NOTT-400), the development of applications of this robust microporous MOF has only grown. In this review, a summary of the applications of MFM-300(Sc), as well as some emerging advanced applications, have been discussed. The adsorption properties of MFM-300(Sc) are presented systematically. Particularly, this contribution is focused on acid and corrosive gas adsorption. In addition, recent applications for catalysis based on the outstanding hemilabile Sc-O bond character are highlighted. Finally, some new research areas are introduced, such as host-guest chemistry and biomedical applications. This highlight aims to showcase the recent advances and the potential for developing new applications of this promising material.

Design of Pore Properties of an Al-Based Metal-Organic Framework for the Separation of an Ethane/Ethylene Gas Mixture via Ethane-Selective Adsorption

A series of Al-based isomorphs (CAU-10H, MIL-160, KMF-1, and CAU-10pydc) were synthesized using isophthalic acid (ipa), 2,5-furandicarboxylic acid (fdc), 2,5-pyrrole dicarboxylic acid (pyrdc), and 3,5-pyridinedicarboxylic acid (pydc), respectively. These isomorphs were systematically investigated to identify the best adsorbent for effectively separating C₂H₆/C₂H₄. All CAU-10 isomorphs exhibited preferential adsorption of C₂H₆ over that of C₂H₄ in mixture. CAU-10pydc exhibited the best C₂H₆/C₂H₄ selectivity (1.68) and the highest C₂H₆ uptake (3.97 mmol g^-1) at 298 K and 1 bar. In the breakthrough experiment using CAU-10pydc, 1/1 (v/v) and 1/15 (v/v) C₂H₆/C₂H₄ gas mixtures were successfully separated into high-purity C₂H₄ (>99.95%), with remarkable productivities of 14.0 L_STP kg^-1 and 32.0 L_STP kg^-1, respectively, at 298 K. Molecular simulations revealed that the exceptional separation performance of CAU-10pydc originated from the increased porosity and reduced electron density of the pyridine ring of pydc, leading to a relatively larger decrease in π-π interactions with C₂H₄ than in the C-H···π interactions with C₂H₆. This study demonstrates that the pore size and geometry of the CAU-10 platform are modulated by the inclusion of heteroatom-containing benzene dicarboxylate or heterocyclic rings of dicarboxylate-based organic linkers, thereby fine-tuning the C₂H₆/C₂H₄ separation ability. CAU-10pydc was determined to be an optimum adsorbent for this challenging separation.

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

[Figure: see text].

The impact of framework flexibility and defects on the water adsorption in CAU-10-H

Aluminum-based metal-organic framework (MOF) CAU-10-H is a promising candidate for heat transformation and water harvesting applications due to its hydrothermal stability, beneficial step-wise water adsorption isotherm and low toxicity. In this study, the effects of the framework flexibility and structural defects on the mechanism of water sorption in CAU-10-H were studied by grand canonical Monte Carlo (GCMC) methods. It was shown by the simulations that the rigid ideal MOF framework is hydrophobic. The account of the linker "flapping" motion during the simulations made the framework more hydrophilic due to unblocking of hydroxyl groups that are inaccessible to water molecules for the rigid structure model. However, this model cannot predict the experimental pressure, at which the step on the adsorption isotherm is observed. Based on this result, we suggested that the presence of structural defects could increase the MOF hydrophilicity. The investigation of the water adsorption using several models of defective structures demonstrated that even a small number of defects shift the calculated position of the step on the adsorption isotherm towards the experimental values. The results obtained in this study emphasize that the controlled synthesis of defective structures is one of the most efficient methods of regulating the MOF adsorption properties.

Understanding the Effect of Water on CO2 Adsorption

Carbon capture from large sources and ambient air is one of the most promising strategies to curb the deleterious effect of greenhouse gases. Among different technologies, CO₂ adsorption has drawn widespread attention mostly because of its low energy requirements. Considering that water vapor is a ubiquitous component in air and almost all CO₂-rich industrial gas streams, understanding its impact on CO₂ adsorption is of critical importance. Owing to the large diversity of adsorbents, water plays many different roles from a severe inhibitor of CO₂ adsorption to an excellent promoter. Water may also increase the rate of CO₂ capture or have the opposite effect. In the presence of amine-containing adsorbents, water is even necessary for their long-term stability. The current contribution is a comprehensive review of the effects of water whether in the gas feed or as adsorbent moisture on CO₂ adsorption. For convenience, we discuss the effect of water vapor on CO₂ adsorption over four broadly defined groups of materials separately, namely (i) physical adsorbents, including carbons, zeolites and MOFs, (ii) amine-functionalized adsorbents, and (iii) reactive adsorbents, including metal carbonates and oxides. For each category, the effects of humidity level on CO₂ uptake, selectivity, and adsorption kinetics under different operational conditions are discussed. Whenever possible, findings from different sources are compared, paying particular attention to both similarities and inconsistencies. For completeness, the effect of water on membrane CO₂ separation is also discussed, albeit briefly.

Fluorinated MIL-101 for carbon capture utilisation and storage: uptake and diffusion studies under relevant industrial conditions

Carbon capture utilisation and storage (CCUS) using solid sorbents such as zeolites, activated carbon and Metal–Organic Frameworks (MOFs) could facilitate the reduction of anthropogenic CO₂ concentration. Developing efficient and stable adsorbents for CO₂ capture as well as understanding their transport diffusion limitations for CO₂ utilisation plays a crucial role in CCUS technology development. However, experimental data available on CO₂ capture and diffusion under relevant industrial conditions is very limited, particularly for MOFs. In this study we explore the use of a gravimetric Dynamic Vapour Sorption (DVS) instrument to measure low concentration CO₂ uptake and adsorption kinetics on a novel partially fluorinated MIL-101(Cr) saturated with different water vapour concentrations, at ambient pressure and temperature. Results show that up to water P/P₀ = 0.15 the total CO₂ uptake of the modified material improves and that the introduction of small amounts of water enhances the diffusion of CO₂. MIL-101(Cr)-4F(1%) proved to be a stable material under moist conditions compared to other industrial MOFs, allowing facile regeneration under relevant industrial conditions.

MIL-101(Cr)-4F(1%) proved to be a stable material under moist conditions compared to other industrial MOFs, with facile regeneration under relevant industrial conditions; plus the introduction of small amounts of water enhances the diffusion of CO₂.

CO2 capture enhancement in MOFs via the confinement of molecules

This review focuses on exploring a new approach to improve the CO₂ adsorption properties of MOFs by confining small amounts of molecules with different nature, such as: water, alcohols, amines, and even aromatic molecules.

Reversible and efficient SO2 capture by a chemically stable MOF CAU-10: experiments and simulations

CAU-10 is an efficient system for SO₂ adsorption, and its great recyclability is given by van der Waals interactions present within its pore.

Robust synthesis routes and porosity of the Al-based metal–organic frameworks Al-fumarate, CAU-10-H and MIL-160

We confirm that the investigated Al-MOFs are robust with respect to reproducible synthesis and concomitant porosity as a prerequisite for applications.

CO2 capture enhancement for InOF-1: confinement of 2-propanol

The confinement of small amounts of i-PrOH demonstrated and enhanced CO₂ capture for InOF-1 as a result of the bottleneck effect and the formation of essential hydrogen bonds.