Processing metal-organic frameworks (MOFs) as films with controllable thickness on asubstrate is increasingly crucial for many applications to realizef unction integration and performance optimization. Herein, we report af acile cathodic deposition process that enables the large-area preparation of uniform films of zeolitic imidazolate frameworks (ZIF-8, ZIF-71, and ZIF-67) with highly tunable thickness ranging from approximately 24 nm to hundreds of nanometers. Importantly,t his oxygen-reduction-triggered cathodic deposition does not lead to the plating of reduced metals (Zn and Co). It is also operable cost-effectively in the absence of supporting electrolyte and facilitates the construction of well-defined submicrometer-sized heterogeneous structures within ZIF films.Metal-organic frameworks (MOFs), ac lass of porous crystalline materials with large surface areas,r egular pore sizes,a nd tailorable surface chemistry, [1] have received considerable attention in av ariety of fields. [2][3][4][5][6][7][8] Form any applications,s uch as separations, [3] energy storage [5] and conversion, [6] chemical sensing, [7] and electronics, [8] it is often necessary to process MOF materials as films on as pecific substrate.A mong methods established for preparing MOF films, [9,10] strategies based on electrochemical synthesis are attractive for many advantages including technological flexibility,scalable preparation, and industrial production potential. [11] Nevertheless,t heir potential for preparing MOF films with precisely tunable morphology and thickness has not been fully explored. These variables,h owever,a re critically important for structure integration and performance optimization in (especially device) applications. [8,9] MOFs could be deposited on the electrode surface anodically [12] or cathodically. [13] In cathodic deposition, reduction of some special molecules or ions (e.g.n itrate ions) on electrode surface results in an increase in pH, which promotes the deprotonation of organic ligands and induces the formation of MOFs.Atfirst glance,cathodic deposition appears to be attractive for the direct synthesis of MOFs on conductive substrates.H owever,r eports on the cathodic deposition of MOFs are comparably few.The challenge arises from the more negative reduction potential of nitrate ions relative to those of some important metal ions,f or example, Zn II ,C o II ,a nd Cu II ,w hich constitute the most extensively studied MOFs. [13b,g] As ar esult, cathodic deposition of these MOF materials is commonly accompanied with plating of the corresponding metals, [13a,e] which is in most cases undesirable.Herein, we report the first cathodic deposition of zeolitic imidazolate framework materials (ZIFs), an important subgroup of MOFs that have been extensively studied owing to their outstanding thermal stability and chemical robustness. [14,15] Our strategy is based on an oxygen reduction triggered-electrochemical-chemical-reaction Scheme responsible for the formation of ZIF materials (Scheme 1). Electrochemical oxyge...

Reductive deposition is an attractive strategy to prepare films of metal–organic frameworks (MOFs), but to cathodically deposit the intergrown dense films of MOFs containing readily reduced metal ions (e.g., Cu2+) without the plating of the corresponding metals still remains a significant challenge. Here, we report the cathodic deposition of metallic copper-free films of two copper-carboxylate MOFs (HKUST-1 and MOF-14). Our strategy relies on the utilization of O2 as probase to electrochemically trigger the crystallization of MOFs. Systematical cyclic voltammetry studies indicate that the favorable synergistic catalytic effects of the acidic copper ions and benzene-1,3,5-tricarboxylic acid ligands on the O2 reduction can positively shift the deposition potential of HKUST-1 significantly to +0.05 V (vs Ag/AgCl), avoiding effectively the plating of metallic copper and facilitating greatly the control over the crystallization kinetics of MOFs. By the further optimization of experimental conditions relevant to reaction temperature, supporting electrolyte, O2 concentration, and working potential, the intergrown dense MOF films with tunable thicknesses were deposited successfully on several commonly used electrodes including the highly oriented pyrolytic graphite, carbon fiber, carbon cloth, and fluorine-doped tin oxide.

We report herein the synthesis of ZIF‐8 hollow spheres with uniform size and shell thickness from monodisperse MOF‐5 cubes via the MOF‐to‐MOF conversion strategy. The ZIF‐8 hollow spheres were obtained by reacting micron‐sized MOF‐5 cubes in the 2‐methylimidazole solution under the optimized experimental conditions. Their chemical composition, crystallinity, porosity, and thermal stability were well characterized and their formation was investigated by time‐dependent electron microscopy and X‐ray diffraction analysis. The porous nature of MOF‐5 and the stronger coordination interaction between 2‐methylimidazole and Zn ions are believed to be responsible for the formation of the ZIF‐8 hollow spheres.

We herein report the formation of two types of ZnO@ZIF core-shell single crystals through the in situ conversion of ZnO particles. The hybrid core-shell single crystals of ZIF-8 and ZIF-71 were obtained by treating 95 nm ZnO particles with 2-methylimidazole and 4,5-dichloroimidazole, respectively, under the optimized experimental conditions. The ZnO cores [a]

No abstract

No abstract

A semitheoretical model based on UNIFAC was proposed to correlate the solubility of solid solute in supercritical fluid (SF) solvent simply and reliably, which does not need critical parameters for solid solutes. The interaction parameters a ij between the SF solvents (such as carbon dioxide, ethylene, and ethane) and the functional groups of solutes were regressed, which is compatible with the vapor−liquid equilibrium (VLE) UNIFAC group-interaction parameters. More efforts and experimental data are needed to obtain a sufficiently large number of interaction parameters for extensive applications. The estimated power exponent of reduced density seems identical for the same solid solute in SF cosolvent homologues. This model could predict the solubility of a solid solute in supercritical CO2 with cosolvents successfully.

No abstract