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

Abstract

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 Zr 6 cluster and pyrene-1,3,6,8-tetracarboxylate (ptc 4À ). 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.

Anisotropic flexibility and rigidification in a TPE-based Zr-MOFs with scu topology

“…The non-interpenetrated structure of Zr-TCPE was further confirmed by low-dose high-resolution transmission electron microscopy (HRTEM) imaging (Fig. 2) [41][42][43] . The low electron dose (only a few electrons per square angstrom) of HRTEM avoids the structural damage of Zr-TCPE under electron beams.…”

Isoreticular Contraction of Cage-like Metal–Organic Frameworks with Optimized Pore Space for Enhanced C2H2/CO2 and C2H2/C2H4 Separations

“…In light of the tunable pore size/shape/volume, − and functionable pore surface, − metal–organic frameworks (MOFs), emerging as a new class of porous solid materials, have attracted a lot of attention in the field of gas adsorption and separation. − The pore system involving pore size/shape/volume and pore space environment can be precisely regulated by substituting the organic linkers with the same symmetry or the inorganic metal nodes based on the isostructural principle and building block strategy, − which in turn endows MOFs with enormous potentials for selective gas separation via the integration of pore size/shape matching and preferential binding interactions toward specific gas molecules. − So far, tremendous endeavors have been devoted to improving the enrichment and separation performance for specific gas molecules, in which the construction of cage-like mixed-ligands MOFs without open metal sites (OMSs), featuring small pore window size, functional pore space, and appropriate pore volume, has represented one of the most effective approaches. − For instance, the pore-space-partition-based MOFs (PSP-MOFs), with cage-like cavities, have shown high performance for gas adsorption and separation, ,− attributed to the relocation of the pore system, stemming from the introduction of the second spacers, involving compartmentalized small pore, functionalized pore space, and reserved appropriate pore volume. The segmented small pore size and functionalized pore surface impart enhanced gas separation through providing dramatically increased adsorbent–adsorbate binding sites toward specific gas molecules, while the preserved appropriate pore volume bestows PSP-MOFs with high gas adsorption performance, thereby making the PSP-MOFs a prominent scaffold for gas adsorption and separation, including C 2 H 2 and CO 2 capture, , C 2 H 2 /CO 2 , − C 2 H 2 /C 2 H 4 /C 2 H 6 , and C 3 H 6 /C 3 H 8 separation. ,, Additionally, the cage-like MOFs without OMSs usually exhibit relatively low adsorption enthalpy compared with the MOFs with O...…”

Phase Engineering of Zirconium MOFs Enables Efficient Osmotic Energy Conversion: Structural Evolution Unveiled by Direct Imaging

“…Metal–organic frameworks (MOFs) feature customizable structures and adjustable functionalities, which can be tailored to suit the demands of diverse applications in catalysis, gas adsorption and separation, drug delivery, and ion transport. − Creating structural defects in MOFs represents an effective strategy to modify their characteristics and enhance their performance in applications. − A class of MOF materials exemplified by UiO-66, constructed from Zr (or Hf) and terephthalic acid (BDC), has garnered widespread attention for their exceptionally high stability. , Because these Zr-BDC-based MOFs possess high node connectivity, typically 12-connected, they are prone to structural defects, making them an excellent platform for “defect engineering”. − …”