Search

Metal-organic frameworks (MOFs) are a new kind of microporous materials whose unique properties make them promising as coatings for solid phase microextraction (SPME). However, previous MOF coatings for SPME exclusively focus on single-linker MOFs, and the selective enrichment of polar or nonpolar targets depends on the polarity of linker on the surface of MOFs, which greatly limits the application of MOF coating for SPME in real samples. Here, we report a hybrid MOF-coated stainless steel fiber for SPME of biomarkers in exhaled breath from gastric cancer patients. Zeolitic imidazolate framework-8-90 (ZIF-8-90) possesses the aldehyde groups and methyl groups in the framework as a model MOF, and eight biomarkers (ethanol, acetone, hexanal, hexanol, nonane, isoprene, heptane, and decane) were used as the target analytes. The ZIF-8-90-coated fiber shows high enrichment efficiency for hydrophilic targets and hydrophobic targets, wide linearity (three orders of magnitude), and low detection limits (0.82-2.64 μg L -1 ). The ZIF-8-90-coated fiber exhibited higher enrichment performance for all the investigated analytes as a result of the synergy of methyl and aldehyde groups, the porous structure, and the suitable pore size of ZIF-8-90 (4-5 Å). The relative standard deviation (RSD) of six repetitions for extractions using the same ZIF-8-90-coated fiber ranged from 2.5 to 7.3%. The reproducibility between the three fibers prepared in parallel varied in the range of 4.8-12% (RSD). The fabricated ZIF-8-90-coated fiber lasted for at least 120 cycles of extraction/desorption/conditioning without an obvious reduction in extraction efficiency and precision. Finally, the developed ZIF-8-90-coated SPME fiber has been successfully used for the analysis of exhaled breath samples from gastric patients with satisfied recoveries (88-106%).

A gas-phase approach to form Zn coordination sites on metal-organic frameworks (MOFs) by vapor-phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution-phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO2 to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200-300 mV. Using element-specific X-ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square-pyramidal geometry with four Zn-N bonds in the equatorial plane and one Zn-OH2 bond in the axial plane. The fine-tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.

Abstract To develop a simple and general method for improving the circularly polarized luminescence (CPL) performances of materials is of great significance. In this work, two pairs of CPL‐active homochiral metal–organic frameworks (MOFs) P/M‐Et and P/M‐Et(Cd) with eta topology are reported. In comparison to the reported isomorphic Zn‐imidazolate MOFs P‐Me and M‐Me, both luminescence dissymmetry factor (glum) and photoluminescence quantum yields (ΦPL) of P‐Et and M‐Et are largely improved by simply changing the methyl group to an ethyl group of ligands in P‐Et and M‐Et. Furthermore, the |glum| values are significantly amplified up to 0.015 from 0.0057 by introducing the non‐luminescent halogenated aromatics, while an enhanced fluorescence efficiency is observed simultaneously (from 27.2% to 47.3%). The figure of merit value is about 40 times larger than that of P‐Me and M‐Me. Similarly, the CPL performances of P/M‐Et(Cd) are improved by about five times after encapsulating fluorobenzene molecules. This work represents a new and simple method for developing CPL‐active MOF materials.

To develop a simple and general method for improving the circularly polarized luminescence (CPL) performances of materials is of great significance. In this work, two pairs of CPL‐active homochiral metal–organic frameworks (MOFs) P/M‐Et and P/M‐Et(Cd) with eta topology are reported. In comparison to the reported isomorphic Zn‐imidazolate MOFs P‐Me and M‐Me, both luminescence dissymmetry factor (glum) and photoluminescence quantum yields (ΦPL) of P‐Et and M‐Et are largely improved by simply changing the methyl group to an ethyl group of ligands in P‐Et and M‐Et. Furthermore, the |glum| values are significantly amplified up to 0.015 from 0.0057 by introducing the non‐luminescent halogenated aromatics, while an enhanced fluorescence efficiency is observed simultaneously (from 27.2% to 47.3%). The figure of merit value is about 40 times larger than that of P‐Me and M‐Me. Similarly, the CPL performances of P/M‐Et(Cd) are improved by about five times after encapsulating fluorobenzene molecules. This work represents a new and simple method for developing CPL‐active MOF materials. [ABSTRACT FROM AUTHOR]

Visible‐light copper photocatalysis has recently emerged as a viable technology for building sustainable synthetic processes. To broaden the applications of phosphine‐ligated copper(I) complexes, we describe herein an effective metal‐organic framework (MOF)‐supported copper(I) photocatalyst for multiple iminyl radical‐mediated reactions. Due to site isolation, the heterogenized copper photosensitizer has a significantly higher catalytic activity than its homogeneous counterpart. Using a hydroxamic acid linker to immobilize copper species on MOF supports affords the heterogeneous catalysts with high recyclability. The post‐synthetic modification sequence on MOF surfaces allows for the preparation of previously unavailable monomeric copper species. Our findings highlight the potential of using MOF‐based heterogeneous catalytic systems to address fundamental challenges in the development of synthetic methodologies and mechanistic investigations of transition‐metal photoredox catalysis. [ABSTRACT FROM AUTHOR]

Due to bimetallic MOFs (metal–organic frameworks) possessing diverse structure topologies and superior properties, herein, we used bimetallic ZIFs (zeolitic imidazole frameworks) of MOFs as precursors via the wet chemical and calcination method to fabricate zinc-embellished Co–Zn@NPC@MWCNT nanocomposites with porous conductive carbon-based networks The abundant carbon defects, zinc evaporation, and N-atom doping resulted in the emergence of dipolar/interface polarization, which is good for dielectric loss. The high porosity and large specific surface area were instrumental in the attenuation of multiple scattering and endowed the absorber with an excellent absorption performance. With merely 15 wt% filled loading and 3.187 mm thickness, the obtained composites under the optimized carbonization temperature (800 °C) exhibited double absorption peaks: the RLmin (minimum reflection loss) reached −76.18 dB@12.88 GHz and −33.09 dB@7.76 GHz, respectively. Moreover, a wide absorption bandwidth can be up to 6.56 GHz (7.2–13.76 GHz) with 3.0 mm thickness, distributed in three frequency bands: 20% of the C band, 100% of the X band, and 29.3% of the Ku band. In addition, the conductive network structure of composites was also beneficial for electromagnetic (EM)-wave absorption. An easy preparation process and low cost can further promote the commercial potential of our obtained bimetallic MOF-based material as an EM-wave absorber. [ABSTRACT FROM AUTHOR]

The fabrication of circularly polarized luminescence (CPL) active materials by self‐assembly is still in its challenge. In this work, a family of homochiral metal–organic frameworks (MOFs) and metal–organic cages (MOCs) are constructed by solvothermal subcomponent self‐assembly. These MOFs feature an eta topology with trifold helical chains, while the MOCs adopt a cubic cage structure. The chiral ligands show two distinct types of conformations: "opened" and "closed" in MOFs and MOCs, respectively. Although homochiral MOFs and MOCs show similar spectra of circular dichroism and photoluminescence with similar quantum yields and lifetimes, the MOFs yield clear CPL signals and the CPL of MOCs are silent. The turn‐on CPL in MOFs achieved by tuning the conformation of ligands and controlling self‐assembly provides a new approach for development of CPL‐active MOF materials. [ABSTRACT FROM AUTHOR]

Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g−1 vs. <0.03 mAh g−1) at −40 °C under reduced pressure of the electrolyte. Liquefied gas electrolytes (LGE) can enable the operation of electrochemical devices in cold conditions but their high vapour pressure poses safety concerns. Here, the authors show that the nano-confinement effect of metal-organic framework allows battery with LGE to work at low temperature and reduced pressure. [ABSTRACT FROM AUTHOR]

In this study, we have successfully synthesized porous CoO–Co@RGO composites using GO and Co-based metal-organic frameworks (MOFs) as precursors. Due to particular structures and advantageous characteristics, the synthesized porous CoO–Co@RGO composites exhibit outstanding electromagnetic (EM) wave absorbing properties with a filler loading of 10 wt.% in wax matrix. The maximum reflection loss (RL) of the prepared porous CoO–Co@RGO was − 3 4. 2 2 dB with 2.1 mm thickness, and the effective absorption bandwidth as wide as 6.24 GHz (11.76–18 GHz), which covers the full Ku-band. Remarkably, the achieved all values of RL were under − 1 0 dB with 1.0–5.0 mm thickness, the corresponding to bandwidth range can be tuned to 13.84 GHz (4.16–18 GHz). The superior absorbing performance is attributed to suitable magnetic loss, high dielectric loss and large attenuation mainly caused by conduction loss and polarization relaxation. In this work, the porous CoO–Co@RGO composites were synthesized by the wet chemical and pyrolysis approach. The maximum reflection loss of porous CoO–Co@RGO composites can reach up to –58.06 dB at 8.32 GHz with 3.24 mm. When the thickness is 2.10 mm, the effective absorption bandwidth can reach up to 6.24 GHz. The range of absorbing bandwidth can be tuned to 13.84 GHz, by adjusting the absorber thickness from 1.0 mm to 5.0 mm. [ABSTRACT FROM AUTHOR]

A gas‐phase approach to form Zn coordination sites on metal–organic frameworks (MOFs) by vapor‐phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution‐phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO2 to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200–300 mV. Using element‐specific X‐ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square‐pyramidal geometry with four Zn−N bonds in the equatorial plane and one Zn‐OH2 bond in the axial plane. The fine‐tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials. [ABSTRACT FROM AUTHOR]

Associated with the unique structure and superior properties of zeolitic imidazolate frameworks (ZIFs) of Co-based metal-organic frameworks (MOFs), we synthesized the MWCNTs@carbonaceous CoO composites of a 3D interconnected network using multi-walled carbon nanotubes (MWCNTs) as decoration through the wet chemical and pyrolysis method. Due to the mutual coordination between proper magnetic loss and strong dielectric loss together with perfect impedance match, the MWCNTs@carbonaceous CoO composites exhibit the maximal reflection loss (RL) value of −50.2 dB with 1.84 mm thickness at 14.3 GHz, absorbing bandwidth (RL ≤ −10 dB) of 13.2 GHz (4.8–18 GHz) with respect to 1.0–4.0 mm thickness range. More importantly, the content of composites added to paraffin matrix is merely 10 wt%. In addition, the synergistic effect between CoO NPs and MWCNTs is also beneficial to the highly efficient electromagnetic (EM) wave absorption of the composites. Therefore, the obtained CoO NPs/MOF-derived composites with lightweight and thin performance can be an attractive candidate of the EM wave absorptive materials. Unlabelled Image • MWCNTs@carbonaceous CoO composite is prepared via wet chemical and pyrolysis method. • The composite can reach −50.2 dB at 14.3 GHz with the thickness of 1.84 mm. • The composite exhibits a bandwidth of 13.2 GHz at RL ≤ −10 dB in the range of 1.0–4.0 mm. • The composite shows a good performance of impedance match. [ABSTRACT FROM AUTHOR]

Copper Photosensitizers, Hydroxamic Acids, Metal-Organic Frameworks, Photoredox Catalysis, Post-Synthetic Modification Back Cover: Metal-Organic Framework Supported Copper Photoredox Catalysts for Iminyl Radical-Mediated Reactions (Angew. Keywords: Copper Photosensitizers; Hydroxamic Acids; Metal-Organic Frameworks; Photoredox Catalysis; Post-Synthetic Modification EN Copper Photosensitizers Hydroxamic Acids Metal-Organic Frameworks Photoredox Catalysis Post-Synthetic Modification 1 1 1 05/09/23 20230515 NES 230515 B A binap-ligated copper iodide dimer b embedded on a metal-organic framework (MOF) was designed as an effective photoredox catalyst by Dan Li, Jian He, and co-workers in their Research Article (e202300233). [Extracted from the article]

Under visible-light irradiation, this heterogenized copper(I) complex promotes multiple iminyl radical-mediated reactions initiated by N-O bond cleavage, with significantly enhanced photocatalytic activity compared to its homogeneous counterparts. Copper Photosensitizers, Hydroxamic Acids, Metal-Organic Frameworks, Photoredox Catalysis, Post-Synthetic Modification Keywords: Copper Photosensitizers; Hydroxamic Acids; Metal-Organic Frameworks; Photoredox Catalysis; Post-Synthetic Modification EN Copper Photosensitizers Hydroxamic Acids Metal-Organic Frameworks Photoredox Catalysis Post-Synthetic Modification 1 1 1 05/09/23 20230515 NES 230515 B A binap-ligated copper iodide dimer b embedded on a metal--organic framework (MOF) was designed as an effective photoredox catalyst by Dan Li, Jian He, and co-workers in their Research Article (e202300233). [Extracted from the article]

UiO-66 metal-organic framework, modified with catechol-substructures and metalated with Cr provides an efficient, completely recyclable and reusable catalyst for oxidation of alcohols to ketones. [ABSTRACT FROM AUTHOR]