An Octacarboxylate-Linked Sodium Metal-Organic Framework with High Porosity.

Alkali metal-based metal-organic frameworks (MOFs) with permanent porosity are scarce because of their high tendency to coordinate with solvents such as water. However, these MOFs are lightweight and bear gravimetric benefits for gas adsorption related applications. In this study, we present the successful construction of a microporous MOF, designated as HIAM-111, built solely on sodium ions by using an octacarboxylate linker. The structure of HIAM-111 is based on 8-connected Na4 clusters and exhibits a novel topology with an underlying 32,42,8-c net. Remarkably, HAM-111 possesses a robust and highly porous framework with a BET surface area of 1561 m2/g, significantly surpassing that of the previously reported Na-MOFs. Further investigations demonstrate that HIAM-111 is capable of separating C2H2/CO2 and purifying C2H4 directly from C2H4/C2H2/C2H6 with high adsorption capacities. The current work may shed light on the rational design of robust and porous MOFs based on alkali metals.

Separation of C2H2/C2H4/C2H6 and C2H2/CO2 in a Nitrogen-Rich Copper-Based Microporous Metal-Organic Framework.

The purification of industrially valuable C2H2 and C2H4 from multicomponent mixtures represents a crucial process in the chemical industry. In this study, we present a copper-based metal-organic framework (L-py-Cu) built on a nitrogen-rich organic linker that is capable of separating C2H2/C2H4/C2H6 and C2H2/CO2 mixtures, therefore producing highly pure C2H4 and C2H2, respectively. L-py-Cu exhibits favorable adsorption of C2H2 and C2H6 over C2H4 and thus achieves one-step C2H4 purification from C2H2/C2H4/C2H6 ternary mixtures, as verified by multicomponent breakthrough measurements. In addition, it can also extract C2H2 from C2H2/CO2 binary mixtures.

Linker Vacancy Engineering of a Robust ftw-type Zr-MOF for Hexane Isomers Separation.

Discrimination of physically similar molecules by porous solids represents an important yet challenging task in industrially relevant chemical separations. Precisely controlled pore dimension and/or tailored pore surface functionality are crucial to achieve high-efficiency separation. Metal-organic frameworks (MOFs) are promising candidates for these challenging separations in light of their structural diversity as well as highly adjustable pore dimension/functionality. We report here a microporous, ftw-type Zr-based MOF structure, HIAM-410 (HIAM=Hoffmann Institute of Advanced Materials), built on hexanuclear Zr6 cluster and pyrene-1,3,6,8-tetracarboxylate (ptc4- ). Its crystallographic structure has been determined using continuous rotation electron diffraction (cRED) technique combined with Rietveld refinement against powder X-ray diffraction data, aided by low-dose high-resolution transmission electron microscopy (HRTEM) imaging. The compound features exceptional framework stability that is comparable to the prototype MOF UiO-66. Interestingly, the linker vacancies in the pristine MOF structure could be partially restored by post-synthetic linker insertion. Its separation capability of hexane isomers is enhanced substantially upon the linker vacancy engineering. The restored structure exhibits efficient splitting of monobranched and dibranched hexane isomers at both room temperature and industrially relevant temperature.

Reticular chemistry guided precise construction of zirconium-pentacarboxylate frameworks with 5-connected Zr6 clusters.

Zirconium-based metal-organic frameworks (Zr-MOFs) have been extensively studied due to their very rich structural chemistry. The combination of nearly unlimited carboxylic acid-based linkers and Zr6 clusters with multiple connectivities has led to diverse structures and specific properties of resultant Zr-MOFs. Herein, we demonstrate the successful use of reticular chemistry to construct two novel Zr-MOFs, HIAM-4040 and HIAM-4040-OH, with zfu topology. Based on a thorough structural analysis of (4,4)-connected lvt-type Zr-tetracarboxylate frameworks and a judicious linker design, we have obtained the first example of a Zr-pentacarboxylate framework featuring unprecedented 5-connected organic linkers and 5-connected Zr6 clusters. Compared with HIAM-4040, a larger Stokes shift is achieved in HIAM-4040-OH via hydroxyl group induced excited-state intramolecular proton transfer (ESIPT). HIAM-4040-OH exhibits high chemical and thermal stability and is used for HClO detection in aqueous solution with excellent sensitivity and selectivity.

Robust Hydrogen-Bonded Organic Framework with Four-Fold Interpenetration for Adsorptive Separation of C2H6/C2H4 and Xe/Kr.

Hydrogen-bonded organic frameworks (HOFs) are an emerging class of porous materials that hold promise for the adsorptive separation of industrially relevant gas mixtures. However, developing HOFs with high thermal stability and resistance to water remains a daunting challenge. We report here a microporous HOF (HIAM-103) assembled from a hexacarboxylate linker (2,4,6-trimethylbenzene-1,3,5-triylisophthalic acid, H6TMBTI). The compound crystallizes in the trigonal crystal system, and its structure is a four-fold interpenetrated network. Upon thermal activation, the single crystals remain intact, allowing for precise determination of the activated structure. HIAM-103 exhibits remarkable thermal and hydrothermal stability. Its microporous channels demonstrate selective adsorption of C2H6 over C2H4 and Xe over Kr, and its separation capability toward mixed gases has been validated by column breakthrough experiments under dry and humid conditions. The preferential gas adsorption sites and separation mechanisms have been uncovered through DFT analysis, which suggests that the methyl group decorated 1D channels are the primary reason for the selective adsorption.

A microporous Zr6@Zr-MOF for the separation of Xe and Kr.

We report here the self-assembly of a she-type zirconium-based metal-organic framework with discrete hexanuclear Zr-oxo clusters residing inside its pore windows. The overall structure features microporosity showing preferential adsorption of Xe over Kr.