Synthesis and Exfoliation of a New Layered Mesoporous Zr-MOF Comprising Hexa- and Dodecanuclear Clusters as Well as a Small Organic Linker Molecule

Abstract

A new layered mesoporous Zr-MOF of composition [Zr30O20(OH)26(OAc)18L18] was synthesized by employing 5-acetamido­isophthalic acid (H2L) using acetic acid as the solvent. The new MOF, denoted as CAU-45, exhibits a honeycomb structure of stacked layers which comprise both hexa- and dodecanucelar zirconium clusters. Its structure was solved from submicrometer-sized crystals by continuous rotation electron diffraction (cRED). Liquid phase exfoliation and size selection were successfully performed on the material.

Three-dimensional electron diffraction for porous crystalline materials: structural determination and beyond

“…With an improved data collection method such as cRED, it is now possible to obtain high-resolution data and perform ab initio structure determination of mesoporous MOFs, as demonstrated recently on mesoporous Ni-MOF BUT-33 94 and Zr-MOF CAU-45. 95 …”

Exfoliation of metal-organic framework nanosheets using surface acoustic waves

“…They mostly rely on the external forces to agitate fluid with high speeds, thus resulting in strong shear forces in the fluid to exfoliate the MOFs. The processing time is varied from ten of minutes to a few hours [24] , [26] , [28] , [29] . However, the thickness distribution is often not uniform, ranging from a few nanometers to hundreds of nanometers [24] , [29] .…”

“…The processing time is varied from ten of minutes to a few hours [24] , [26] , [28] , [29] . However, the thickness distribution is often not uniform, ranging from a few nanometers to hundreds of nanometers [24] , [29] . They also have drawbacks including high energy consumption, inability to obtain high yields of monolayer nanomaterials, and difficulty in production of large-scale single layer sheets.…”

Synthesis of two new Hf‐MOFs with UiO‐66 and CAU‐22 structure employing 2,5‐pyrazinedicarboxylic acid as linker molecule.

“…In addition two mixed cluster MOFs have been reported: CAU-45/MIP-206 (MIP = material of the Institute of Porous Materials of Paris), containing the hexanuclear and the dodecanuclear cluster and Zr-MTBC (MTBC 4À = methane-tetrakis(p-biphenyl carboxylate), containing hexanuclear and cubic {M 8 O 8 (OH) 4 } clusters. [19][20][21] The existence of the latter cluster must be regarded with great caution since chemically insensible ZrÀ Zr distances are found. [21] Zirconium and Hafnium have nearly the same ionic radius, due to the lanthanide contraction, and therefore the chemical behaviour of both metals is similar.…”

“…For carboxylate based Zr‐MOFs only a few other IBUs like ZrO 7 ‐polyhedra in [Zr(dobdc)(bz) x ](H 2 O) x (dobdc 4− =2,5‐dioxylatoterepthalate, bz=benzoate), [4] infinite ZrO‐chains in the MIL‐140 series (MIL=Matériaux de l′Institut Lavoisier), [15] the dodecanuclear {Zr 12 (O) 8 (OH) 8 (μ‐OH) 6 } cluster [16] or infinite chains of condensed hexanuclear {Zr 6 O 4 (OH) 4 (μ‐OH) 2 } clusters in CAU‐22 ([Zr 6 O 4 (OH) 8 (H 2 O) 2 (HCO 2 ) 2 (PzDC) 3 ], CAU=Christian‐Albrechts‐Universität) [17] and CAU‐27 ([Zr 5 O 4 (OH) 4 (CH 3 CO 2 ) 4 (BDC) 2 ]) [18] are known (Figure 1). In addition two mixed cluster MOFs have been reported: CAU‐45/MIP‐206 (MIP=material of the Institute of Porous Materials of Paris), containing the hexanuclear and the dodecanuclear cluster and Zr‐MTBC (MTBC 4− =methane‐tetrakis(p‐biphenyl carboxylate), containing hexanuclear and cubic {M 8 O 8 (OH) 4 } clusters [19–21] . The existence of the latter cluster must be regarded with great caution since chemically insensible Zr−Zr distances are found [21] …”