Polypyrene Porous Organic Framework for Efficiently Capturing Electron Specialty Gases

A HF-resistant perfluorinated porous polymer for the separation of electronic specialty gases

A perfluorinated porous polymer, PFPP-1, featuring large SBET (1068 m2 g-1) and ultrahigh fluorine content (35.6 at%), was synthesized to accomplish high HF resistance and selective adsorption of F-gases. Enhanced dipole interactions and optimal F-gas/N2 selectivity highlight PFPP-1's potential for efficient recovery of electronic specialty gases in sustainable electronics.

A Microporous Hydrogen-Bonded Organic Framework with Open Pyrene Sites Isolated by Hydrogen-Bonded Helical Chains for Efficient Separation of Xenon and Krypton

Achieving efficient xenon/krypton (Xe/Kr) separation in emerging hydrogen-bonded organic frameworks (HOFs) is highly challenging because of the lack of gas-binding sites on their pore surfaces. Herein, we report the first microporous HOF (HOF-FJU-168) based on hydrogen-bonded helical chains, which prevent self-aggregation of the pyrene core, thereby preserving open pyrene sites on the pore surfaces. Its activated form, HOF-FJU-168a is capable of separating Xe/Kr under ambient conditions while achieving an excellent balance between adsorption capacity and selectivity. At 296 K and 1 bar, the Xe adsorption capacity of HOF-FJU-168a reached 78.31 cm3/g, with an Xe/Kr IAST selectivity of 22.0; both values surpass those of currently known top-performing HOFs. Breakthrough experiments confirmed its superior separation performance with a separation factor of 8.6 and a yield of high-purity Kr (>99.5 %) of 184 mL/g. Furthermore HOF-FJU-168 exhibits excellent thermal and chemical stability, as well as renewability. Single-crystal X-ray diffraction and molecular modeling revealed that the unique electrostatic surface potential around the open pyrene sites creates a micro-electric field, exerting a stronger polarizing effect on Xe than on Kr, thereby enhancing host-Xe interactions.

Molecular Mechanism Behind the Capture of Fluorinated Gases by Metal-Organic Frameworks

Fluorinated gases (F-gases) play a vital role in the chemical industry and in the fields of air conditioning, refrigeration, health care, and organic synthesis. However, the direct emission of waste gases containing F-gases into the atmosphere contributes to greenhouse effects and generates toxic substances. Developing porous materials for the energy-efficient capture, separation, and recovery of F-gases is highly desired. Recently, as a highly designable porous adsorbents, metal-organic frameworks (MOFs) exhibit excellent selective sorption performance toward F-gases, especially for the recognition and separation of different F-gases with highly similar properties, showing their great potential in F-gases control and recovery. In this review, we discuss the capture and separation of F-gases and their azeotropic, near-azeotropic, and isomeric mixtures in various application scenarios by MOFs, specifically classify and analyze molecular interaction between F-gases and MOFs, and interpret the mechanisms underlying their high performance regarding both adsorption capacity and selectivity, providing a repertoire for future materials design. Challenges faced in the transformation research roadmap of MOFs adsorbent separation technologies toward F-gases are also discussed, and areas for future research endeavors are highlighted.

Metal-Organic Framework-Based NF3 Nanotrap for the Separation of NF3 and CF4

As an electronic specialty gas, nitrogen trifluoride (NF3) has been widely used in the semiconductor, photovoltaic, and display industries. However, NF3 in industrial settings is typically mixed with CF4, and the distillation method commonly used for their separation consumes significant energy. Herein, we propose a novel NF3 nanoadsorber featuring relatively proximal unsaturated metal sites. The potential field overlap between the two unsaturated metal centers creates an NF3-affinitive environment. The adsorption mechanism of NF3 molecules in the metal-organic frameworks (MOFs) was investigated through density functional theory (DFT) optimization. The results from ideal adsorbed solution theory (IAST) calculations and breakthrough experiments reveal that the MOF-based NF3 nanotrap possesses the highest adsorption capacity and excellent NF3/CF4 selectivity among the physically adsorptive materials reported to date. This work presents a novel solution for the separation and purification of NF3, contributing to the field of gas separation technology.

Cost-Effective, Hydrogen-Rich, and Ultramicroporous Metal-Organic Framework for Efficient Separation of SF6 from N2

It is essential for the industry to create an adsorbent that combines a high capacity with selectivity to achieve the effective separation of SF6 from gas mixtures. In this study, we prepared a cost-effective nickel-based metal-organic framework (MOF), Ni(BTC)(BPY), which features hydrogen-rich ultramicroporous channels specifically designed for separating SF6/N2 gas mixtures. The findings from the adsorption experiments demonstrated that Ni(BTC)(BPY) achieved a remarkable SF6 adsorption capacity of 5.08 mmol g-1 and an ideal adsorbed solution theory SF6/N2 selectivity of 382. This effectively resolves the trade-off encountered in the development of adsorbents between capacity and selectivity. Theoretical calculations indicated the optimal adsorption sites for SF6 within the pore channels. The strong interactions between the F atoms in SF6 and the numerous H atoms in the channels account for the superior SF6 adsorption performance of this material. Breakthrough experiments provided additional evidence that the MOF can completely separate SF6/N2 mixtures, positioning it as an excellent candidate for recovering SF6 from these gas mixtures.

Ultramicroporous Metal-Organic Framework Featuring Multiple Polar Sites for Efficient Xenon Capture and Xe/Kr Separation

Efficient adsorption separation of xenon/krypton (Xe/Kr) mixtures is an important technological challenge due to their similar sizes and shapes. Herein, we report an ultramicroporous metal-organic framework (MOF), ZJU-Bao-302a, with pore sizes close to the kinetic diameter of Xe and pore surfaces lined with a high density of polar sites, including methyl groups, amines, and uncoordinated oxygen atoms. The synergistic effect of these polar sites enables ZJU-Bao-302a to exhibit a high Xe uptake of 2.77 mmol g-1 and a balanced Xe/Kr selectivity of 14.6 under ambient conditions. Dynamic breakthrough experiments demonstrate the material's capability to efficiently separate Xe/Kr mixtures (20/80) as well as capture Xe at ultralow concentrations (400 ppmv) from nuclear reprocessing exhausts, achieving a superior dynamic Xe capacity of 24.2 mmol kg-1. Density functional theory calculations reveal that the localized polar groups/atoms in ZJU-Bao-302a provide more effective recognition sites for Xe than Kr, enhancing the thermodynamic selectivity. This study highlights the importance of integrating tailored pore sizes and dense polar sites in metal-organic frameworks for developing high-performance Xe/Kr separation adsorbents.

Room-Temperature Synthesis of a Fluorine-Functionalized Nanoporous Organic Polymer for Highly Efficient SF6 Adsorption and Separation

Sulfur hexafluoride (SF6) is widely used in the power industry and significantly contributes to the greenhouse effect, necessitating the development of efficient materials for SF6 capture, particularly fluorine-containing materials. However, existing fluorine-containing materials often require complex monomers and high synthesis temperatures. Herein, we report the synthesis of a fluorine-functionalized carbazole-based nanoporous organic polymer (CNOP-7) at room temperature, using commercially available 4,4'-bis(9H-carbazole-9-yl)-1,1'-biphenyl and 1,1,1-trifluoroacetone. CNOP-7 contains 14.7% fluorine atoms and exhibits a high specific surface area of 1270 m2·g-1, demonstrating excellent SF6 adsorption and separation performance. The SF6/N2 selectivity of CNOP-7 reaches 107 at 273 K and 73 at 298 K. Furthermore, dynamic breakthrough experiments confirm that CNOP-7 can efficiently and repeatedly separate SF6 from SF6/N2 mixtures. Molecular simulations reveal the mechanism behind its efficient separation. This work offers fresh perspectives on the development and fabrication of adsorbents for efficient SF6 sequestration.

Room-temperature synthesis of a fluorine-functionalized nanoporous organic polymer for efficient SF6 separation

Addressing the environmental impact of SF6, we synthesized a fluorine-functionalized triphenylamine-based nanoporous organic polymer, ANOP-8, at room temperature using N,N,N',N'-tetraphenylbenzidine and 2,3,4,5,6-pentafluorobenzaldehyde. ANOP-8, which incorporates 14.86% fluorine, has a BET surface area of 694 m2 g-1 and a robust C-C structure. It achieves SF6/N2 selectivities of 65 and 51 at 298 K and 1 bar through ideal adsorbed and breakthrough experiments, respectively. Molecular simulations have revealed the adsorption mechanisms, underscoring the potential of fluorinated polymers in developing future adsorbents for toxic gases.

Non-CO2 greenhouse gas separation using advanced porous materials

Global warming has become a growing concern over decades, prompting numerous research endeavours to reduce the carbon dioxide (CO2) emission, the major greenhouse gas (GHG). However, the contribution of other non-CO2 GHGs including methane (CH4), nitrous oxide (N2O), fluorocarbons, perfluorinated gases, etc. should not be overlooked, due to their high global warming potential and environmental hazards. In order to reduce the emission of non-CO2 GHGs, advanced separation technologies with high efficiency and low energy consumption such as adsorptive separation or membrane separation are highly desirable. Advanced porous materials (APMs) including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), porous organic polymers (POPs), etc. have been developed to boost the adsorptive and membrane separation, due to their tunable pore structure and surface functionality. This review summarizes the progress of APM adsorbents and membranes for non-CO2 GHG separation. The material design and fabrication strategies, along with the molecular-level separation mechanisms are discussed. Besides, the state-of-the-art separation performance and challenges of various APM materials towards each type of non-CO2 GHG are analyzed, offering insightful guidance for future research. Moreover, practical industrial challenges and opportunities from the aspect of engineering are also discussed, to facilitate the industrial implementation of APMs for non-CO2 GHG separation.

Halogen-engineered metal–organic frameworks enable high-performance electrochemical glucose sensing

A series of isomorphically halogen-engineered MOFs are synthesized for electrochemical glucose sensing. By tuning the electronegativity of the halogen atom on the MOF skeleton, the sensing performance are significantly improved.