ZIF-8 Films Research Articles

Development of a novel magnetic molecularly imprinted polymer coating using porous zeolite imidazolate framework-8 coated magnetic iron oxide as carrier for automated solid phase microextraction of estrogens in fish and pork samples

A high-performance magnetic molecularly imprinted polymer (MIP) coating using zeolite imidazolate framework-8 coated magnetic iron oxide (Fe3O4@ZIF-8) as a carrier was developed for simultaneous automated solid phase microextraction of four estrogens in 24 food samples. The coating material, abbreviated as MZMIP, was synthesized through time-efficient layer-by-layer assembling of ZIF-8 and MIP film on Fe3O4 particles. It was characterized and automatically coated on the surface of SPME fibers by electromagnetic bonding. The extraction performance, reusability, repeatability, and validity of the MZMIP–SPME system was evaluated for high-throughput analysis of estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2). Various factors affecting the quality of MZMIP coating were optimized. Compared with traditional magnetic MIP coating based on Fe3O4@SiO2 carrier, the MZMIP coating exhibited high extraction capacity and quick adsorption and desorption kinetics to E1, E2, E3, and EE2 owing to the larger amount of imprinting sites in MZMIP. Under optimum conditions, the proposed system requires only 25min for pretreatment of all 24 samples (62.5s per sample). The limits of detection and quantitation of the proposed automated system for analysis were found to range from 0.4 to 1.7 and 1.1 to 6.2ngg−1, respectively. During analysis of spiked fish and pork, the new coating showed better recovery and selectivity compared with Fe3O4@SiO2@MIP (MMIP) and commercially available SPME. The results indicated that the MZMIP coating could be effectively employed for pretreatment of ultra-trace level of estrogens in food.

Aqueous solution synthesis of ZIF-8 films on a porous nylon substrate by contra-diffusion method

ZIF-8 films were prepared on both sides of nylon membrane in aqueous solutions using a stoichiometric ratio of Zn2+ and 2-methylimidazole (hmim) by a contra-diffusion method. Both ammonium hydroxide solution and porous nylon membrane play a crucial role in promoting ZIF-8 crystallization and film formation. Ammonium hydroxide solution added in the hmim solution deprotonates hmim, and the nylon membrane separates the Zn2+ and hmim aqueous solutions with different diffusion rates through its pores, leading to appropriate concentration gradients of hmim and zinc nitrate required for ZIF-8 nucleation and growth. The synthesis conditions were systematically investigated. ZIF-8 films prepared with a Zn2+:hmim:NH4+ molar ratio of 1:2:32 at room temperature for 24h exhibited an intergrown ZIF-8 layer on hmim side with a thickness of ca. 2.5μm, and gas permeation confirmed the film was continuous and compact with a H2/N2 ideal selectivity of 4.6.

Solvent-free synthesis of supported ZIF-8 films and patterns through transformation of deposited zinc oxide precursors

Film processing and patterning techniques are a prerequisite to fully exploit the potential of metal–organic frameworks (MOFs) in integrated applications. We report a solvent-free approach for the synthesis of ZIF-8 thin films and patterns through the reaction of ZnO films with melted 2-methylimidazole.

Metal-Organic Framework ZIF-8 Films As Low-κ Dielectrics in Microelectronics

ZIF-8 films were deposited on silicon wafers and characterized to assess their potential as future insulators (low-κ dielectrics) in microelectronics. Scanning electron microscopy and gas adsorption monitored by spectroscopic ellipsometry confirmed the good coalescence of the crystals, the absence of intergranular voids, and the hydrophobicity of the pores. Mechanical properties were assessed by nanoindentation and tape tests, confirming sufficient rigidity for chip manufacturing processes (elastic modulus >3 GPa) and the good adhesion to the support. The dielectric constant was measured by impedance analysis at different frequencies and temperatures, indicating that κ was only 2.33 (±0.05) at 100 kHz, a result of low polarizability and density in the films. Intensity voltage curves showed that the leakage current was only 10–8 A cm2 at 1 MV cm–1, and the breakdown voltage was above 2 MV cm–1. In conclusion, metal-organic framework ZIF-8 films were experimentally found to be promising candidates as low-κ ...

Engineering ZIF‐8 Thin Films for Hybrid MOF‐Based Devices

Patterned metal-organic framework, ZIF-8 thin films can be generated by using standard photolithography or via selective growth with the aid of microcontact printing. The alternate chemical deposition (of ZIF-8) and physical deposition (of metallic materials) allow the insertion of metal layers in the ZIF-8 film that could serve as multifunctional chemical sensors for vapors and gases.

Contra-diffusion synthesis of ZIF-8 films on a polymer substrate

ZIF-8 films were successfully prepared on a flexible nylon substrate with a contra-diffusion synthesis method, and gas permeation experiments indicated that the films were continuous and compact.

Metal–organic frameworks: promising materials for improving the open circuit voltage of dye-sensitized solar cells

Metal–organic frameworks (MOFs) were used for the first time to coat TiO2 to enhance the open circuit voltage (Voc) of dye-sensitized solar cells (DSC). ZIF-8 was selected as a representative MOF for a case study. After a growth time of 30 min, a very thin ZIF-8 film was coated on TiO2 with a thickness of about 2 nm. A linear relationship between the thickness of ZIF-8 coating layer and the Voc is found, and the value of Voc was increased by 55 and 66 mV for the dye N719 and D131, respectively. Mott–Schottky measurement demonstrated that the enhanced Voc was not caused by the changed conduction band edge of TiO2 due to its possible coordination with 2-methyl imidazole. The electrochemical impedance spectra and I–V characteristics of the cells measured under dark conditions indicated the increased Voc could be ascribed to the inhibited interfacial charge recombination due to the introduction of ZIF-8 shell material. Although the amount of adsorption of dyes for the TiO2/ZIF-8 electrode was increased significantly, the core/shell structure inhibited the injection of electrons from dyes into the conduction band edge of TiO2, which decreased the short circuit current.

Synthesis of Zeolitic Imidazolate Framework Films and Membranes with Controlled Microstructures

Zeolitic imidazolate frameworks (ZIFs) are hybrid organic-inorganic microporous materials that exhibit zeolite-like structures and can be synthesized with a wide range of pore sizes and chemical functionality. ZIFs as thin films and membranes are of interest for their applications in sensors and gas separation. Here, we report a method for ZIF film and membrane fabrication, based on support surface modification and in situ solvothermal growth, which has potential for general application to other ZIF membranes. Our simple surface modification method results in strong covalent bonds between α-Al(2)O(3) supports and imidazolate ligands, which promote the heterogeneous nucleation and growth of ZIF crystals. The microstructure of ZIF-8 films can be controlled by controlling the pH of the growth solution. ZIF-7 films were fabricated to demonstrate the potential for general applicability of our method. Finally, the separation performance of several ZIF-8 membranes was evaluated, revealing molecular sieving behavior with an ideal selectivity for H(2)/CH(4) of 13.