Topology-Guided Design for Sc-soc-MOFs and Their Enhanced Storage and Separation for CO2 and C2-Hydrocarbons

Efficient CO2 Capture and Separation in MOFs: Effect from Isoreticular Double Interpenetration

Severe CO2 emissions has posed an increasingly alarming threat, motivating the development of efficient CO2 capture materials, one of the key parts of carbon capture, utilization, and storage (CCUS). In this study, a series of metal-organic frameworks (MOFs) named Sc-X (X = S, M, L) were constructed inspired by recorded MOFs, Zn-BPZ-SA and MFU-4l-Li. The corresponding isoreticular double-interpenetrating MOFs (Sc-X-IDI) were subsequently constructed via the introduction of isoreticular double interpenetration. Grand canonical Monte Carlo (GCMC) simulations were adopted at 298 K and 0.1-1.0 bar to comprehensively evaluate the CO2 capture and separation performances in Sc-X and Sc-X-IDI, with gas distribution, isothermal adsorption heat (Qst), and van der Waals (vdW)/Coulomb interactions. It is showed that isoreticular double interpenetration significantly improved the interactions between adsorbed gases and frameworks by precisely modulating pore sizes, particularly observed in Sc-M and Sc-M-IDI. Specifically, the Qst and Coulomb interactions exhibited a substantial increase, rising from 28.38 and 22.19 kJ mol-1 in Sc-M to 43.52 and 38.04 kJ mol-1 in Sc-M-IDI, respectively, at 298 K and 1.0 bar. Besides, the selectivity of CO2 over CH4/N2 was enhanced from 55.36/107.28 in Sc-M to 3308.61/7021.48 in Sc-M-IDI. However, the CO2 capture capacity is significantly influenced by the pore size. Sc-M, with a favorable pore size, exhibits the highest capture capacity of 15.86 mmol g-1 at 298 K and 1.0 bar. This study elucidated the impact of isoreticular double interpenetration on the CO2 capture performance in MOFs.

Sacrificial-Hydroxamate-Enabled Sizable Crystallization of Scandium Carboxylate Metal-Organic Frameworks

Starting from labile hydroxamic acid ligands that are strong chelators, here, we implemented a sacrificial modulating strategy to prepare a series of scandium carboxylate metal-organic frameworks. Overcoming conventional syntheses that use excessive carboxylate modulators, the present strategy greatly reduces the organics required and produces large single crystals of several Sc-MOFs for X-ray crystallography.

Pore Environmental Modification by Alkoxy Groups in Pore-Space-Partitioned Metal-Organic Frameworks to Achieve Gas Uptake-Selectivity Balance

Due to the trade-off barrier between high storage capacity and high selectivity, the controllable and systematic design of metal-organic frameworks (MOFs) aiming at performance optimization is still challenging. Herein, considering the effectiveness of alkoxy group functionalization and a pore-space partition strategy, a series of rigid Mg-pacs-MOFs (SNNU-10-n, n = 1-6) with flexible side chains are built for the first time, realizing systematic pore environmental modification. The steric hindrance effects, electron-donating ability, and the flexibility of alkoxy groups are considered as key factors, which lead to a regular change of gas adsorption capacity and selectivity. Notably, methoxy-modified SNNU-10-1 with moderately high storage capacities of C₂H₂ (139.4 cm³ g^-1), C₂H₄ (100.4 cm³ g^-1), CO₂ (105.0 cm³ g^-1), and high selectivity values for equimolar C₂H₂/CH₄ (431.8), C₂H₄/CH₄ (164.2), and CO₂/CH₄ (16.1) mixture separation at 273 K and 100 kPa achieves an ideal gas uptake-selectivity balance. Breakthrough experiments verified that it could effectively separate the above-mentioned mixtures under ambient conditions, and GCMC simulation provides a deep understanding of methoxy group functionalization. Undoubtedly, this work not only realizes controllable regulation of gas adsorption behavior but also proves the validity of improving selectivity by alkoxy groups in those platforms with high gas-uptake potential to overcome the trade-off barrier.

Highly selective C2H2 and CO2 capture based on two new ZnII-MOFs and fluorescence sensing of two doped MOFs with EuIII

Two Zn(ii)-based MOFs have been constructed. The activated Zn-MOF1 and Zn-MOF2 show selective separation of C2H2 and CO2 over CH4. Eu@Zn-MOF1 and Eu@Zn-MOF2 were obtained by adding EuIII ions and showed selectivity to Fe3+ ions in aqueous solution.

Facile synthesis disposable MOF membrane filter: Growth of NH2-MIL-125 (Ti) on filter paper for fast removal of organophosphorus pesticides in aqueous solution and vegetables

Metal-organic frameworks (MOFs) have great potential to remove pesticide residues. However, the lack of affinity between the materials and target and the process of trivial sample preparation resulted in limited removal efficiency. Here, we report a one-pot method for the fast preparation of NH₂-MIL-125 (Ti)-based filter paper to synthesise NH₂-MIL-125 (Ti)-based filter paper membranes. The NH₂-MIL-125 (Ti)-based filter paper membrane takes advantage of π-π interactions between the organophosphorus pesticides (OPPs) and the benzene ring of MOFs. The affinity of amino groups and metal Ti for phosphorus atoms in the OPPs exhibits rapid removal efficiency for three OPPs, imidan, fenthion, and fenitrothion. The isothermal adsorption results for imidan, fenthion, and fenitrothion were consistent with the Langmuir, Freundlich, and Langmuir models, respectively. The kinetic results for imidan, fenthion, and fenitrothion agreed with the pseudo-second-order kinetic model, and the removal efficiency reached equilibrium within 1 min. There was no significant change in the adsorption capacity of OPPs in different pH solutions (pH = 2-10). Compared with that of MOFs, the NH₂-MIL-125 (Ti)-based filter paper membrane removal efficiency of OPPs is the same, and it also has better removal efficiency in actual spinach samples. As a result, the sample pretreatment procedure was simplified using a low-cost and simple-to-synthesize disposable NH₂-MIL-125 (Ti)-based filter paper membrane, samples' quick separation and the simultaneous fast removal of OPPs.

Micropore Regulation in Ultrastable [Sc3O]-Organic Frameworks for Acetylene Storage and Purification

High storage capacity, high separation selectivity, and high structure stability are essential for an idea gas adsorbent. However, it is not easy to achieve all three at the same time, even for the promising metal-organic framework (MOF) adsorbents. We demonstrate herein that robust [Sc₃O]-organic frameworks could be regulated by a micropore combination strategy for high-performance acetylene adsorption. Under the same solvent system with formic acid as a modulator, similar tritopic ligands extend [Sc₃O(COO)₆] trigonal-prismatic clusters to generate SNNU-5-Sc and SNNU-150-Sc adsorbents. Notably, the two Sc-MOFs can keep their architectures over 24 h in water at different pH values (2-12) or at 90 °C. Modulated by the linker symmetry, the final stacking metal-organic polyhedral cages produce open window sizes of about 10 Å for SNNU-5-Sc and 5 Å + 7 Å for SNNU-150-Sc. Due to such micropore combinations, SNNU-5-Sc exhibits a top-level C₂H₂ uptake of 211.2 cm³ g^-1 (1 atm and 273 K) and SNNU-150-Sc shows high C₂H₂/CH₄, C₂H₂/C₂H₄, and C₂H₂/CO₂ selectivities of 80.65, 4.03, and 8.19, respectively, under ambient conditions. Dynamic breakthrough curves obtained on a fixed-bed column and grand canonical Monte Carlo (GCMC) simulations further support their prominent acetylene storage and purification performance. High framework stability, storage capacity, and separation selectivity make SNNU-5-Sc and SNNU-150-Sc ideal acetylene adsorbents in practical applications.

Sc(iii)-Based metal–organic frameworks

In the universe of MOFs, their construction with Sc(iii) is rather limited. This highlight shows the exciting chronological development of Sc(iii)-MOFs which have afforded promising applications due to their exceptional chemical stability.

Construction of two novel non-penetrating Co-MOFs derived from designed 2,4,6-tri(2,4-dicarboxyphenyl) pyridine: synthesis, structure and gas adsorption properties

The strategy of extending ligands and reducing symmetry provide a facile access to obtain a wide variety of linkers for the construction of MOFs bearing diverse structures and intriguing properties....

Finely Tuning Tridentate Carboxylic Acids for the Construction of Rod Scandium Metal-Organic Frameworks with High Chemical Stability and Selective Gas Adsorption

By systematic ligand tuning for control of the secondary building units, the use of tridentate carboxylic acid to construct the rod scandium metal-organic framework NTUniv-55 (NTUniv = Nantong University) with high chemical stability and interesting selective gas adsorption was reported.

Clip-off Chemistry: Synthesis by Programmed Disassembly of Reticular Materials*

Bond breaking is an essential process in chemical transformations and the ability of researchers to strategically dictate which bonds in a given system will be broken translates to greater synthetic control. Here, we report extending the concept of selective bond breaking to reticular materials in a new synthetic approach that we call Clip‐off Chemistry. We show that bond‐breaking in these structures can be controlled at the molecular level; is periodic, quantitative, and selective; is effective in reactions performed in either solid or liquid phases; and can occur in a single‐crystal‐to‐single‐crystal fashion involving the entire bulk precursor sample. We validate Clip‐off Chemistry by synthesizing two topologically distinct 3D metal‐organic frameworks (MOFs) from two reported 3D MOFs, and a metal‐organic macrocycle from metal‐organic polyhedra (MOP). Clip‐off Chemistry opens the door to the programmed disassembly of reticular materials and thus to the design and synthesis of new molecules and materials.

Introducing High Density of Very Active Sites and Stepwise Postmodification for Tailoring the Porosity of Highly Demanding Cr3+-Based Metal-Organic Frameworks

Chromium(III)-based metal-organic frameworks (Cr-MOFs) are highly robust and porous and have been very attractive in a wide range of investigations. However, the harsh direct synthetic conditions not only impede the synthesis of new Cr-MOFs but also restrict the introduction of functional groups into them. Postsynthetic modification has somewhat alleviated such difficulties; nevertheless, it still suffered from procedures that are tedious and conditions that are not mild, which often result in low concentration of the functional groups introduced. To overcome these shortcomings, here, in this paper, we supplied a new route and prepared a benzyl alcohol functionalized Cr-SXU-2 from the judiciously designed benzyl alcohol functionalized Fe-SXU-2 through solvent-assisted metal metathesis strategy. The functionalized Cr-SXU-2 shows well-preserved crystallinity, porosity, and high chemical stability. The benzyl alcohol group can be converted into a very active benzyl bromide group in an almost quantitative yield and thus for the first time produce the benzyl bromide functionalized MOF, Cr-SXU-2-Br, in which the -Br group can be exchanged by a nucleophilic group. As a proof of concept, -N₃ was introduced and transformed into other active sites via "click reaction" to further tailor the interior of Cr-SXU-2. All these functionalized Cr-MOFs showed improved adsorption performance in contrast to the nonfunctionalized one. This step-by-step postmodification process not only diversifies the functionalization of robust MOFs but also opens a new route to employ many different functional groups in the demanding highly stable Cr-MOF platforms.

Viologen-Based Cationic Metal-Organic Framework for Efficient Cr2O72- Adsorption and Dye Separation

A novel cationic metal-organic framework composed of {Cu₂(COO)₄} paddle-wheel units and a tetracarboxylic viologen derivative, namely, {[Cu₂(bdcbp)(H₂O)₂]·2NO₃·2H₂O}_n (Cu-CMOF, H₄bdcbpCl₂ = 1,1'-bis(3,5-dicarboxyphenyl)-4,4'-bipyridinium dichloride), has been successfully synthesized and structurally characterized. In Cu-CMOF, the {Cu₂(COO)₄} unit and viologen derivative both act as four-connected nodes forming an ssb-type cationic network with 4².8⁴ topology, in which the positive charges are distributed on the organic viologen moieties. Deeper insight of the structure indicates that the 3D architecture of Cu-CMOF can be seen as packing of a 26-faceted polyhedral cage and two cuboid cages. Notably, Cu-CMOF displays a highly efficient anion exchange ability for capture and removal of anionic pollutants. UV-vis absorption spectra and digital images demonstrate that Cu-CMOF is capable of adsorbing the dichromate anion and anionic dyes effectively, such as methyl orange (MO^-), Congo red (CR^2-), and New Coccine (NC^3-). Meaningfully, anionic dyes (MO^-, CR^2-, and NC^3-) can be efficiently and selectively removed by Cu-CMOF in the presence of cationic dye methylene blue (MLB⁺). Such behaviors of anionic pollutant adsorption and dye separation are mainly caused by an ion-exchange process facilitated by the large cavity and decentralized distribution of positive charge in Cu-CMOF.

A Dy6-cluster-based fcu-MOF with efficient separation of C2H2/C2H4 and selective adsorption of benzene

A stable Dy-MOF was constructed based on hexanuclear clusters, and contains F-decorated pores and reveals separation performance for C₂H₂/CH₄, C₂H₄/CH₄ and C₂H₂/C₂H₄ and selective adsorption of benzene/cyclohexane and benzene/toluene.

Construction of three new Co(ii)-organic frameworks based on diverse metal clusters: highly selective C2H2 and CO2 capture and magnetic properties

Three Co(ii)-MOFs have been synthesized. The desolvated frameworks of 2 and 3 exhibit good adsorption selectivity for C₂H₂ and CO₂ over CH₄ at 273 and 298 K. Moreover, 1–3 show that there exist antiferromagnetic interactions between metal ions.

Two scandium-based coordination polymers: rapid ultrasound-assisted synthesis, crystal transformation, and catalytic properties

Assisted by ultrasound waves, a Sc-based coordination polymer CP 1 was synthesized successfully. With 1 as the precursor, another stable CP 2 can be obtained by single-crystal to single-crystal transformation and 2 exhibited good catalytic activities.

Uncommon thioether-modified metal–organic frameworks with unique selective CO2 sorption and efficient catalytic conversion

Two novel 3D MOFs were synthesized successfully. In particular, MOF 1 was found to selectively adsorb CO₂ from the mixture of CH₄/CO₂ and perform as an excellent recyclable catalyst to fix CO₂ into cyclic carbonate.

Structural diversity and photocatalytic activity of six Co(ii)/Ni(ii) complexes with three flexible phenylenediacetate isomers

Six coordination polymers show structural diversity have been reported. Their photocatalytic for the degradation of dye have been well studied.

Efficient C2Hn Hydrocarbons and VOC Adsorption and Separation in an MOF with Lewis Basic and Acidic Decorated Active Sites

To help address efficient separation of C₂H_n light hydrocarbons and C₂H₂/CO₂ in the chemical industry, the self-assembly via an azolate-carboxylate ligand and Co(II) ion gave rise to a new porous MOF material, [Co(btzip)(H₂btzip)]·2DMF·2H₂O (1) (H₂btzip = 4,6-bis(triazol-1-yl)isophthalic acid). In the MOF, the pores are modified by rich uncoordinated triazolyl Lewis basic N atoms and acidic -COOH groups, which strengthen interactions with C₂H_n hydrocarbons and CO₂ molecules, leading to high adsorption amounts for C₂H_2, C₂H₄, C₂H₆, and CO₂ and remarkable separation efficiency for C₂H_n-CH₄, CO₂-CH₄, and C₂H₂-CO₂ mixtures, as confirmed by breakthrough experiments on the realistic gas mixtures. The MOF also reveals outstanding selective adsorption ability for benzene/toluene, methanol/1-propanol, methanol/2-propanol, and 2-propanol/1-propanol isomers. Molecular simulations disclose the different adsorption sites in the MOF for various adsorbates.

Acid-Base-Resistant Metal-Organic Framework for Size-Selective Carbon Dioxide Capture

The development of practical porous materials for the selective capture of CO₂ from flue gas and crude biogas is highly critical for both environment protection and energy safety. Here, a novel metal-organic framework (FJI-H29) has been prepared, which not only has excellent acid-base resistance but also possesses polar micropores (3.4-4.3 Å) that can match CO₂ molecules well. FJI-H29 can selectively capture CO₂ from N₂ and CH₄ with excellent separation efficiency and suitable adsorption enthalpy under ambient conditions. Breakthrough experiments further confirm its practicability for both CO₂/N₂ and CO₂/CH₄ separation. All of these confirm FJI-H29 is a practical CO₂ adsorbent. Modeling calculations reveal that the confinement effect of micropores and the polar environment synergistically promotes the selective adsorption of CO₂, which will provide a potential strategy for the synthesis of a practical metal-organic framework for CO₂ capture.