Synthesis and Self‐Assembly of Monodispersed Metal‐Organic Framework Microcrystals

Abstract

Self-assembly of monodispersed objects with sizes ranging from nanometers to millimeters offers a useful route to new functional materials and devices featuring two-dimensional (2D) or three-dimensional (3D) ordered structures that are not easily achieved with conventional photolithographybased microfabrication techniques. [1] Beyond classic spheres, [2] non-spherical building blocks [3] such as ellipsoids, [4] dumbbells, [5] rods, [6] stars, [7] octapods, [8] and polyhedrons [9][10][11][12] have attracted increasing interest due to advances in colloidal synthesis that enable the precise control over the size and shape of colloidal particles. In particular, selfassembly of polyhedrons made of crystalline materials such as metals, [9] oxides, [10] and semiconductors [11] has been extensively investigated from both the theoretical [12] and experimental viewpoints in recent years.Metal-organic frameworks (MOFs), a new class of crystalline materials, are synthesized by assembly of metal ions or clusters with organic linkers. [13] MOFs display permanent microporous structures with large surface areas, regular but tunable cavity sizes, and tailorable chemistry, and thus show great promise for wide applications including gas storage, [14] molecule separation, [15] heterogeneous catalysis, [16] chemical sensing, [17] and drug delivery. [18] In the past few years, many efforts have been undertaken in MOF synthesis to control the size [19][20][21][22] and shape [23] of MOF crystals since these parameters can significantly impact certain properties of bulk materials, for example, gas sorption, [19] and indeed are critical for biological applications. [18,20] Meanwhile, MOF crystals with small sizes can be processed easily into thin films and membranes through dip-coating [24] or spin-coating, [25] and further, oriented MOF films can also be prepared with crystals of regular shapes and with the aid of the Langmuir-Blodgett (LB) technique. [26] In this regard, MOF crystals with uniform size and shape will facilitate not only the control over the thickness of oriented films but also the formation of 2D or 3D ordered structures by bottom-up self-assembly. Nevertheless, relevant work is just beginning, and only 2D self-assembly of MOF microcrystals has been realized recently. [27] Challenges in this emerging area are the synthesis of monodispersed MOF crystals with uniform sizes and shapes as well as the exploration of appropriate assembly techniques.Here, we report 1) the acetic acid-modulated synthesis of monodispersed octahedral microcrystals of a zirconium-carboxylate MOF material, UiO-66 (UiO stands for University of Oslo), 2) the preparation of oriented MOF films with controlled thickness based on the assembly of large-area 2D monolayers of a microcrystal, and 3) the formation of longrange 3D superlattices of MOF microcrystals through a sedimentation technique (Scheme 1). UiO-66 is a chemically robust and thermally stable MOF material and was first synthesized in intergrown crystal form by Lillerud et al. [28] Subsequen...

Observing the Growth of Metal–Organic Frameworks by in Situ Liquid Cell Transmission Electron Microscopy

“…27 Either 250 or 500 nm spacer chips were used to set the nominal thickness of the liquid flowing through the cell. UiO-66 and ZIF-8 particles were synthesized as previously described 28,29 (see Supporting Information for details) and analyzed by TEM and powder X-ray diffraction (PXRD) ( Figures S1 and S2). UiO-66(Zr) MOF is composed of Zr(IV)-based nodes and 1,4-benzenedicarboxylate (bdc) linkers.…”

A metal–organic framework/α-alumina composite with a novel geometry for enhanced adsorptive separation

“…25 UiO-66 used in this study was synthesized via the typical solvo-thermal method with minor modification. 11,26,27 Its characteristic XRD pattern (see Supplementary Fig. S2) and N 2 adsorption-desorption isotherms (see Supplementary Fig.…”

An overview: synthesis of thin films/membranes of metal organic frameworks and its gas separation performances

“…Several techniques have been described in the literature to synthesize MOF membranes, including in situ synthesis and secondary (seeded) growth. 24,[46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] In situ involves only one step synthesis for fabricating membranes but does not offer the microstructure control and substrate independence of secondary (seeded) growth. [54][55][56][57] The attention of interested readers in these MOF thin lms' syntheses could be directed to these articles.…”