In situ growth of ZIF-8 into solid-state nanochannels

Metal-organic framework-mediated synthesis of hierarchical layered double hydroxide for high-efficiency enrichment of phosphopeptides

When applied as adsorbents for phosphopeptides enrichment, two-dimensional (2D) layered double hydroxides (LDHs) are usually limited by the disadvantages of buried affinity sites and reduced specific surface area. Multifarious exfoliation strategies have been implemented to compensate for these deficiencies, but tedious exfoliation process cannot meet the requirements of LDHs as high-efficiency adsorbents. Incorporating LDHs with three-dimensional (3D) template can avoid tedious exfoliation and produce hierarchical LDHs with large specific surface area and massive affinity sites. Herein, a hierarchical LDH (denoted as Fe₃O₄@ZIF-8@Zn-Ga LDH) was prepared by metal-organic framework (MOF)-mediated synthesis strategy, and a magnetic solid-phase extraction (MSPE) platform was constructed and employed for phosphopeptides enrichment with high efficiency. The unique 3D structure and abundant metal nodes of MOF provide 3D template and metal sources for in-situ nucleation and generation of LDH. Large specific surface area and massive exposed Zn and Ga endow Fe₃O₄@ZIF-8@Zn-Ga LDH with high enrichment efficiency toward phosphopeptides from complicated biological samples. With the aid of mass spectrometry (MS) techniques, we profiled endogenous or global phosphopeptides from human saliva and serum, which proved the practical application value of this material.

Enzyme-Encapsulated Zeolitic Imidazolate Frameworks Formed Inside the Single Glass Nanopore: Catalytic Performance and Sensing Application

Metal-organic frameworks (MOFs) can improve the stability and activity of enzymes under the MOF encapsulation. However, it remains a challenge to explore the effects of the MOF environment on enzymatic activity in a confined space. In this work, we immobilized the enzyme inside a glass nanopore to study the catalytic activity and stability of the enzyme in the MOF environment. Horseradish peroxidase (HRP) is encapsulated in zeolitic imidazolate framework-90 (ZIF-90) and zeolitic imidazolate framework-8 (ZIF-8), which are used as the catalytic platforms. The HRP can catalyze 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) molecules to generate ABTS⁺ ions, and the change of the transmembrane ion current will be monitored in real time. As the concentration of H₂O₂ increases, the amount of produced ABTS⁺ will increase; thus, the ionic current increases. The effects of the MOF structure on enzyme activity and stability are also investigated. The HRP encapsulated in the MOF and modified inside the nanopore provides a novel and unlabeled design for studying enzymatic catalysis in a confined environment, which should have extensive applications in chemical-/bio-sensing, electrocatalysis, and fundamental electrochemistry.

Observation of early ZIF-8 crystallization stages with X-ray absorption spectroscopy

The present study investigates early stages of ZIF-8 crystallization up to 5 minutes post mixing of precursor solutions. Dispersive X-ray Absorption Spectroscopy (DXAS) provides a refined understanding of the evolution of the coordination environment during ZIF-8 crystallization. Linear Combination Analysis (LCA) suggests tetrakis(1-methylimidazole)zinc2+ to be a suitable and stable mononuclear structure analogue for some early stage ZIF-8 intermediates. Our results pave the way for more detailed studies on physico-chemical aspects of ZIF-8 crystallization to better control tailoring ZIF-8 materials for specific applications.

Nanochannels regulating ionic transport for boosting electrochemical energy storage and conversion: a review

Electrochemical power sources, as one of the most promising energy storage and conversion technologies, provide great opportunities for developing high energy density electrochemical devices and portable electronics. However, uncontrolled ionic transport in electrochemical energy conversion, typically undesired anion transfer, usually causes some issues degrading the performance of energy storage devices. Nanochannels offer an effective strategy to solve the ionic transport problems for boosting electrochemical energy storage and conversion. In this review, the advantages of nanochannels for electrochemical energy storage and conversion and the construction principle of nanochannels are introduced, including ion selectivity and ultrafast ion transmission of nanochannels, which are considered as two critical factors to achieve highly efficient energy conversion. Recent advances in applications of nanochannels in lithium secondary batteries (LSBs), electrokinetic energy conversion systems and concentration cells are summarized in detail. Nanochannels exist in the above systems in two typical forms: functional separator and electrode protective layer. Current research on nanochannel-based LSBs is still at the early stage, and deeper and broader applications are expected in the future. Finally, the remaining challenges of nanochannel fabrication, performance improvement, and intelligent construction are presented. It is envisioned that this paper will provide new insights for developing high-performance and versatile energy storage electronics based on nanochannels.