Crystal Growth of ZIF-8, ZIF-67, and Their Mixed-Metal Derivatives

Abstract

A facile method to produce zeolitic imidazolate frameworks (ZIF-8, ZIF-67, and solid-solution ZIFs (mixed Co and Zn)) is reported. ZIF crystals are produced via a reaction-diffusion framework (RDF) by diffusing an outer solution at a relatively high concentration of the 2-methyl imidazole linker (HmIm) into an agar gel matrix containing the metal ions (zinc(II) and/or cobalt(II)) at room temperature. Accordingly, a propagating supersaturation wave, initiated at the interface between the outer solution and the gel matrix, leads to a precipitation front with a gradient of crystal sizes ranging between 100 nm and 55 μm along the reaction tube. While the precipitation fronts of ZIF-8 and ZIF-67 travel the same distance for the same initial conditions, ZIF-8 crystals therein are consistently smaller than the ZIF-67 crystals due to the disparity of their rate of nucleation and growth. The effects of the temperature, the concentration of the reagents, and the thickness of the gel matrix on the growth of the ZIF crystals are investigated. We also show that by using RDF we can envisage the formation mechanism of the ZIF crystals, which consists of the aggregation of ZIF nanospheres to form the ZIF-8 dodecahedrons. Moreover, using RDF, the formation of a solid-solution ZIF via the incorporation of Co(II) and Zn(II) cations within the same framework is achieved in a controlled manner. Finally, we demonstrate that doping ZIF-8 by Co(II) enhances the photodegradation of methylene blue dye under visible light irradiation in the absence of hydrogen peroxide.

Liesegang Banding for Controlled Size and Growth of Zeolitic‐Imidazolate Frameworks

“…A new method for the synthesis of MOF‐199 and ZIF‐8 via a reaction–diffusion framework (RDF) was recently developed by our group. RDF is a method that involves continuous precipitation reactions triggered by diffusing a concentrated solution of one coprecipitate (outer electrolyte) into a tube containing a gel medium with the other coprecipitate (inner electrolyte) .…”

Metal‐Organic‐Framework‐Derived MCo2O4 (M=Mn and Zn) Nanosheet Arrays on Carbon Cloth as Integrated Anodes for Energy Storage Applications

“…The magnified SEM image in Figure 2e showed that the synthesized composites were with similar shapes as the CoÀ MOF precursor and the thickness of the MnÀ CoÀ MOF sheets was about 150 nm. Corresponding EDS spectrum of the composites in Figure 2f demonstrated 4 were observed, suggesting that the materials prepared are pure Co-based spinel metal oxides. This is in consistent with the results of previous reports.…”

“…[1][2][3] Many kinds of meso-or microporous compounds such as carbonaceous materials, metal oxides, and metal phosphides have already been prepared by using MOFs structure as template or precursor from various processes. [4][5][6][7][8] Compared with common materials prepared from traditional solid state or chemical liquid methods, these porous compounds derived from MOFs template have evidently improved advantages including regular porosity size, large specific surface area, topological diversity and shearing ability, leading to their worldwide applications in gas storage and separation, light capture, energy conversion and storage devices, catalysis and chemical sensor and so on. [9][10][11] Spinel structured cobalt-based oxides have been extensively investigated as alternative anode materials for electrochemical energy storage devices such as supercapacitors (SCs) and lithium ion batteries (LIBs).…”

Simultaneous Modulation of Composition and Oxygen Vacancies on Hierarchical ZnCo2O4/Co3O4/NC‐CNT Mesoporous Dodecahedron for Enhanced Oxygen Evolution Reaction

“…The SEM image reveals a distinct rhombic dodecahedral structure of ZnCo‐ZIFs with a uniform size (≈1.13 μm, Figure B and C), which is about twice the size of ZIF‐67 and ZIF‐8 (Figure S2 A–D in the Supporting Information). This can be ascribed to the weaker coordination ability of Co 2+ with 2‐methylimidazole, which may affect the nanocrystal nucleation of ZnCo‐ZIFs . TGA/DTG results for ZnCo‐ZIF precursors in Figure D show significant weight losses (18.5 %) at 572 °C, corresponding to sharp exothermic peaks; this is ascribed to the loss of guest molecules and thermal decomposition of ZIF structures .…”