Synthesis of zeolitic imidazolate framework-8 using an electric field in a gelled medium

Using the ion migration in various gel mediums governed by a direct electric field is a well-known technique, especially in analytical chemistry, to separate charged chemical species. This approach is also suitable for generating different-sized crystals and controlling the pattern formation in gels. Here we present a synthesis of zeolitic imidazolate framework-8 in an agarose gel driven by a direct electric field. We investigate the effect of an applied electric current on the macroscopic pattern formed in the gel, morphology, size, and dispersity of the ZIF-8 crystals. Upon increasing the electric current, the average size of the particles and dispersity of the samples decreased along the gel tube from the liquid-gel interface of the anodic side. This trend is opposite to the results obtained in synthesising particles utilizing only diffusion for mass transport. The electric field caused peak-doubling in the X-ray diffraction (XRD) pattern. To support the experimental observations, we developed a reaction-diffusion-migration model, which qualitatively describes the pattern formation observed in experiments.A direct electric field can be used to control the synthesis of the metal-organic framework in a gelled medium. The average size and dispersity of the crystals can be directed by the electric field strength

Periodic Precipitation of Zeolitic Imidazolate Frameworks in a Gelled Medium

Formation of spatially periodic patterns is a ubiquitous process in nature and man-made systems. Periodic precipitation is the oldest type of pattern formation, in which the formed colloid particles are self-assembled into a sequence of spatially separated precipitation zones in solid hydrogels. Chemical systems exhibiting periodic precipitation mostly comprise oppositely charged inorganic ions. Here, we present a new sub-group of this phenomenon driven by the diffusion and reaction of several transition metal cations (Zn2+, Co2+, Cd2+, Cu2+, Fe2+, Mn2+, and Ni2+) with an organic linker (2-methylimidazole) producing periodic precipitation of zeolitic imidazolate frameworks. In some cases, the formed crystals reached the size of ∼50 μm showing that a gel matrix can provide optimal conditions for nucleation and crystal growth. We investigated the effect of the gel concentration and solvent composition on the morphology of the pattern. To support the experimental observations, we developed a reaction-diffusion model, which qualitatively describes the spatially periodic pattern formation. © 2022 The Authors. Published by American Chemical Society

Application of a chemical clock in material design: chemically programmed synthesis of zeolitic imidazole framework-8

Here we show a time-programmed and autonomous synthesis of zeolitic imidazole framework-8 (ZIF-8) using a methylene glycol-sulfite clock reaction. The induction period of the driving clock reaction, thus, the appearance of the ZIF-8 can be adjusted by the initial concentration of one reagent of the chemical clock. The autonomously synthesized ZIF-8 showed excellent morphology and crystallinity

Formation of Precipitation Ellipsoidal Disks and Spheres in the Wake of a Planar Diffusion Front.

Pattern formation is one of the examples of self-organization. In the generation of patterns, the coupling between the mass transport of the chemical species and their chemical reactions plays an important role. Periodic precipitation (Liesegang phenomenon) is a type of pattern formation in which layered precipitation structures form in the wake of the diffusion front. Here, we show a new type of precipitation pattern formation in zeolitic imidazolate framework-67 in a solid hydrogel column in a test tube manifested in the generation of precipitation ellipsoidal disks and spheres in the wake of the planar diffusion front of the outer electrolyte (2-methylimidazole). To increase the probability of the emergence of ellipsoidal disks and spheres, the surfaces of the borosilicate test tubes were chemically treated and functionalized. To support the experimental findings, we developed a reaction-diffusion model that qualitatively describes the formation of precipitate ellipsoidal disks and spheres in a test tube

Effects of radial injection and solution thickness on the dynamics of confined A + B -> C chemical fronts

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Chemical flowers: Buoyancy-driven instabilities under modulated gravity during a parabolic flight

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Influence of thermal effects on buoyancy-driven convection around autocatalytic chemical fronts propagating horizontally.

The spatiotemporal dynamics of vertical autocatalytic fronts traveling horizontally in thin solution layers closed to the air can be influenced by buoyancy-driven convection induced by density gradients across the front. We perform here a combined experimental and theoretical study of the competition between solutal and thermal effects on such convection. Experimentally, we focus on the antagonistic chlorite-tetrathionate reaction for which solutal and thermal contributions to the density jump across the front have opposite signs. We show that in isothermal conditions the heavier products sink below the lighter reactants, providing an asymptotic constant finger shape deformation of the front by convection. When thermal effects are present, the hotter products, on the contrary, climb above the reactants for strongly exothermic conditions. These various observations as well as the influence of the relative weight of the solutal and thermal effects and of the thickness of the solution layer on the dynamics are discussed in terms of a two-dimensional reaction-diffusion-convection model parametrized by a solutal R(C) and a thermal R(T) Rayleigh number.Journal Articleinfo:eu-repo/semantics/publishe

Effects of gravity modulation on the dynamics of a radial A + B -> C reaction front

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