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.

In-MOF-Derived Hierarchically Hollow Carbon Nanostraws for Advanced Zinc-Iodine Batteries

Hollow carbon materials are regarded as crucial support materials in catalysis and electrochemical energy storage on account of their unique porous structure and electrical properties. Herein, an indium-based organic framework of InOF-1 can be thermally carbonized under inert argon to form indium particles through the redox reaction between nanosized indium oxide and carbon matrix. In particular, a type of porous hollow carbon nanostraw (HCNS) is in situ obtained by combining the fusion and removal of indium within the decarboxylation process. The as-synthesized HCNS, which possesses more charge active sites, short and quick electron, and ion transport pathways, has become an excellent carrier for electrochemically active species such as iodine with its unique internal cavity and interconnected porous structure on the tube wall. Furthermore, the assembled zinc-iodine batteries (ZIBs) provide a high capacity of 234.1 mAh g^-1 at 1 A g^-1 , which ensures that the adsorption and dissolution of iodine species in the electrolyte reach a rapid equilibrium. The rate and cycle performance of the HCNS-based ZIBs are greatly improved, thereby exhibiting an excellent capacity retention rate. It shows a better electrochemical exchange capacity than typical unidirectional carbon nanotubes, making HCNS an ideal cathode material for a new generation of high-performance batteries.

Harnessing Shape Complementarity for Upgraded Cyclohexane Purification through Adaptive Bottlenecked Pores in an Imidazole-Containing MOF

Shape complementarity is a biological craft for precisely binding substrates at protein-protein interfaces. An analogy to such a function can be drawn conceptually for crystalline porous solids; yet the manifested entities are rare in reticular chemistry. The bottleneck-shaped pores carved out of a metal-organic framework, Zn(MIBA)₂ (aka. MAF-stu-13), can perfectly accommodate benzene molecules. Remarkably, its framework adapts to the optimal guest binding-the enhanced host-guest interactions in the neck in turn minimize the guest-guest repulsion in the pore to the extent it turns into attraction-as demonstrated by the combined X-ray structural and DFT computational studies. This adaptive material can be used for liquid-phase production of ultrahigh-purity (≥99 %) cyclohexane, achieving a balance between uptake capacity and separation selectivity and surpassing the performances of other porous and nonporous crystals reported recently (e.g. product purity 99.4 % vs. 97.5 % to date).

In Situ Aliovalent Nickle Substitution and Acidic Modification of Nanowalls Promoted Proton Conductivity in InOF with 1D Helical Channel

Proton-conductive materials have attracted increasing attention because of their broad explorations in chemical sensors, water electrolysis, fuel cells, and biological systems. Especially, metal-organic frameworks (MOFs) have been demonstrated to be extremely promising candidates as proton-exchange membrane (PEM) fuel cells. Compared with other configurations, MOFs with one-dimensional (1D) channels have the characteristics of enhancing the host-guest interaction and promoting the anisotropic motion of proton carriers in restricted volume, which are beneficial for acquiring rich proton sources and forming successive hydrogen bonds to improve proton conductivity. We are endeavored to screen and find a helical three-dimensional (3D) framework InOF-1, namely, [In₂(OH)₂(BPTC)]·6H₂O (BPTC^4- = 3,3',5,5'-biphenyl tetracarboxylate), as a typical 1D-channel MOF, which is pristinely grafted with spirally distributed -OH groups on the channel surface. Accompanied by an aliovalent substitution Ni(II) for In(III), isostructural NiOF-1 ([Ni₂(BPTC)(HCOOH)₂]·3H₂O) is successfully prepared and massive formic acids are anchored at interior walls, which are interacted with adsorbed water molecules via the formation of stronger O-H···O bonds. This interaction between host-guest molecules and dynamics of lattice water has already led to a remarkable conductivity of InOF-1 (σ = 7.86 × 10^-3 S/cm at 328 K under 95% RH). The synergistic effect of the acidic-modified nanowall, contracted volume, and enhanced adsorption of water molecules in the NiOF-1 channel contributes to a high conductivity value of 3.41 × 10^-2 S/cm (at 328 K under 95% RH). Moreover, the proton conduction mechanism is further visually presented by molecular dynamic (MD) simulation. In contrast to InOF-1, aliovalent-substituted and acidic-modified NiOF-1 has a stronger host-guest interaction and more abundant hydrogen-bond networks, resulting in shorter proton migration distances and more frequent proton hopping, in agreement with the experimental results.

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.

Bottleneck Effect Explained by Le Bail Refinements: Structure Transformation of Mg-CUK-1 by Confining H2O Molecules

The structure transformation of Mg-CUK-1 due to the confinement of H₂O molecules was investigated. Powder X-ray diffraction (PXRD) patterns were collected at different H₂O loadings and the cell parameters of the H₂O-loaded Mg-CUK-1 material were determined by the Le Bail strategy refinements. A bottleneck effect was observed when one hydrogen-bonded H₂O molecule per unit cell (18% relative humidity (RH)) was confined within Mg-CUK-1, confirming the increase in the CO₂ capture for Mg-CUK-1.

Confined benzene within InOF-1: contrasting CO2 and SO2 capture behaviours

Benzene confinement enhances the CO₂ capture while decreases the SO₂ capture within InOF-1 due to the competition among molecules for the preferential adsorption sites. Pore channel view of CO2Bz@InOF-1b (left) and SO2⋯Bz@InOF-1b (right) systems.

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.

Confined toluene within InOF-1: CO2 capture enhancement

The confinement of small amounts of toluene demonstrated an enhanced CO₂ capture for InOF-1 as a result of a bottleneck effect and synergistic interactions.

Relevance of hydrogen bonding in CO2 capture enhancement within InOF-1: an energy and vibrational analysis

DFT and experimental in situ results postulate four plausible CO₂ adsorption mechanism for MeOH-functionalised InOF-1.

Solvent effects on the crystal structure of silver pentacyanocyclopentadienide: supramolecular isomerism and solvent coordination

Several coordination polymers of silver(i)-pentacyanocyclopentadienide (PCC) were studied by X-ray diffraction to examine the effects of different solvents on supramolecular isomerism of the PCC-ligand. While alcohols yield supramolecular isomers of [Ag(PCC)] without coordination of solvent molecules, less polar solvents show coordinate binding. The influence of solvent polarity can be observed by a gradual change in the lattice structure featuring distinct motifs.

Confinement of H2O and EtOH to enhance CO2 capture in MIL-53(Al)-TDC

EtOH adsorption–desorption properties of MIL-53(Al)-TDC along with the confinement of small amounts of water to enhance its CO₂ capture, and the reversible capture of iodine are presented in this article.

Chiral metal–organic frameworks constructed from four-fold helical chain SBUs for enantioselective recognition of α-hydroxy/amino acids

Three chiral 3D metal–carboxylate frameworks have been successfully synthesized, featuring four-fold helical metal chains as SBUs. Co-MOFs could recognize enantio-selectively α-hydroxy/amino acids by the change of CD signals.

In situ analysis of the adsorption behaviors of CO2 on the surface of MIL-91(Al)

We have successfully synthesized layered MIL-91(Al) via a reflux method and investigated the adsorption behaviors of CO₂ on its surface.

CO2 capture in a carbazole-based supramolecular polyhedron structure: the significance of Cu(ii) open metal sites

Upon the removal of coordinated H₂O and DMF molecules to the paddlewheel of MOP 4 (followed by FTIR), it showed very interesting CO₂ capture properties at 196 K.

Confined methanol within InOF-1: CO2 capture enhancement

The CO₂ capture in InOF-1 was enhanced by confining small amounts of MeOH. DFT calculations coupled with forcefield based-MC simulations revealed that such an enhancement is due to an increase of the degree of confinement.

Confinement of alcohols to enhance CO2 capture in MIL-53(Al)

CO₂ capture of MIL-53(Al) was enhanced by confining small amounts of MeOH and i-PrOH within its micropores.

Selective adsorption behaviour of carbon dioxide in OH-functionalized metal–organic framework materials

The theoretically optimal adsorption locations in hydroxyl (OH)-decorated metal–organic frameworks show that the captured CO₂ molecules interact with the cis-μ₂-OH groups in an end-on mode, which shows a moderate to weak hydrogen bond.

Water Adsorption Properties of NOTT-401 and CO2 Capture under Humid Conditions

The water-stable material NOTT-401 was investigated for CO₂ capture under humid conditions. Water adsorption properties of NOTT-401 were studied, and their correlation with CO₂ sequestration at different relative humidities (RHs) showed that the CO₂ capture increased from 1.2 wt % (anhydrous conditions) to 3.9 wt % under 5% RH at 30 °C, representing a 3.2-fold improvement.