Hydroamination of Phenylacetylene with Aniline over Gold Nanoparticles Embedded in the Boron Imidazolate Framework BIF-66 and Zeolitic Imidazolate Framework ZIF-67

Dynamic behavior of metal nanoparticles in MOF materials: analysis with electron microscopy and deep learning

Electron microscopy is a key characterization technique for nanoscale systems, and electron microscopy images are typically recorded and analyzed in terms of the morphology of the objects under study in static mode. The emerging current trend is to analyze the dynamic behavior at the nanoscale observed during electron microscopy measurements. In this work, the study of the stability of MOF structures with different compositions and topologies under conditions of an electron microscope experiment revealed an unusual dynamic behavior of M NPs formed due to the electron-beam-induced transformation of specific frameworks. The transition to the liquid phase led to spatial movement, rapid sintering, and an increase in the M NPs size within seconds. In the case of copper nanoparticles, instantaneous sublimation was observed. The dynamic behavior of Co NPs was analyzed with a computational framework combining deep learning and classic computer vision techniques. The present study for the first time revealed unique information about the stability of a variety of MOFs under an electron beam and the dynamic behavior of the formed M NPs. The formation of Fe, Ni, Cu, and Co NPs was observed from a molecular framework with a specific subsequent behavior - a stable form for Fe, excessive dynamics for Co, and sublimation/condensation for Cu. Two important outcomes of the present study should be mentioned: (i) electron microscopy investigations of MOF samples should be made with care, as decomposition under an electron beam may lead to incorrect results and the appearance of "phantom" nanoparticles; and (ii) MOFs represent an excellent model for fundamental studies of molecular-to-nano transitions in situ in video mode, including a number of dynamic transformations.

Selective and ratiometric fluorescence sensing of bisphenol A in canned food based on portable fluorescent test strips

In this study, a conversion method and molecular imprinting technology were used to design molecularly imprinted polymers (MIP)-based ratiometric fluorescence test papers. The ZnO quantum dots (ZnO QDs) acted as the background quantum dots and ZIF-8 raw material. Carbon dots (CDs) were used as the identification signals. The imprinting layer achieved a selective function. Therefore, a ZnO@ZIF-8/CDs@MIPs sensor was designed for the detection of Bisphenol A (BPA). The sensor exhibited a fast response time for BPA detection. In addition, the sensor demonstrated that effective detection of BPA can still be achieved in complex environments. The detection limit of this sensor was 0.778 nM with a linear range of 0-60 nM. The corresponding test solutions exhibited clear changes from blue to yellow. The selectivity experiments results demonstrated that ZnO@ZIF-8/CDs@MIPs only exhibit excellent selective recognition effect for BPA. ZnO@ZIF-8/CDs@MIPs-2 was used for the detection of BPA in canned food and compared with the results of HPLC detection of BPA. The two spiked recovery ranges were 96.58-102.04% and 97.43-103.82%, respectively. In addition, the prepared ZnO@ZIF-8/CDs@MIPs-2 test paper visually recognized BPA under ultraviolet light. This study provides guidelines for the design and application of fluorescent test papers for quick detection in practical applications.

Unsupported nanoporous gold catalyst for highly selective hydroamination of alkynes

An efficient and highly selective heterogeneous catalyst system for hydroamination of alkynes was developed using unsupported gold nanopores (AuNPore) for the first time. The AuNPore-catalyzed highly regioselective hydroamination of alkynes proceeded smoothly without any additive and solvent under mild conditions (rt-50 °C) to yield Markovnikov imines in satisfactory to excellent yields. No gold leached from AuNPore during the hydroamination of alkynes. Moreover, the catalyst was easily recovered and reused without any loss of catalytic activity. A one-pot, two-step procedure using a single AuNPore catalyst has been devised to produce secondary amines derived from readily available alkynes and anilines with high atom efficiency.

The Impact of Functionality and Porous System of Nanostructured Carriers Based on Metal–Organic Frameworks of UiO-66-Type on Catalytic Performance of Embedded Au Nanoparticles in Hydroamination Reaction

New methods for the preparation of metal–organic frameworks UiO-66 and NH2-UiO-66 with a hierarchical porous structure were developed using the MW-assisted technique under atmospheric pressure. The synthesized nanostructured meso-UiO-66 and meso-NH2-UiO-66 matrices were utilized as Au nanoparticle carriers. The resulting Au@meso-UiO-66 and Au@NH2-UiO-66 nanohybrids were studied in the reaction of phenylacetylene hydroamination with aniline into imine ([phenyl-(1-phenylethylydene)amine]) for the first time. Their catalytic behavior is significantly determined by a combination of factors, such as a small crystal size, micro–mesoporous structure, and functionality of the UiO-66 and NH2-UiO-66 carriers, as well as a high dispersion of embedded gold nanoparticles. The Au@meso-UiO-66 and Au@NH2-UiO-66 nanocatalysts demonstrate high activities (TOF), with conversion and selectivity values over 90. This excellent catalytic performance is comparable or even better than that demonstrated by heterogeneous systems based on conventional inorganic and inorganic supports known from the literature.