HKUST-1 is a metal–organic framework (MOF) which plays a significant role in both applicative and basic fields of research, thanks to its outstanding properties of adsorption and catalysis but also because it is a reference material for the study of many general properties of MOFs. Its metallic group comprises a pair of Cu2+ ions chelated by four carboxylate bridges, forming a structure known as paddle-wheel unit, which is the heart of the material. However, previous studies have well established that the paddle-wheel is incline to hydrolysis. In fact, the prolonged exposure of the material to moisture promotes the hydrolysis of Cu–O bonds in the paddle-wheels, so breaking the crystalline network. The main objective of the present experimental investigation is the determination of the details of the structural defects induced by this process in the crystal, and it has been successfully pursued by coupling the electron paramagnetic resonance spectroscopy with other more commonly considered techniques, such as X-ray diffraction, surface area estimation, and scanning electron microscopy. Thanks to this original approach we have recognized three stages of the process of decomposition of HKUST-1, and we have unveiled the details of the corresponding equilibrium structures of the paddle-wheels at the atomic scale level

Carbon nanodots are known for their appealing optical properties, especially their intense fluorescence tunable in the visible range. However, they are often affected by considerable issues of optical and structural heterogeneity, which limit their optical performance and limit the practical possibility of applying these nanoparticles in several fields.Here we developed a synthesis method capable of producing a unique variety of carbon nanodots displaying an extremely high visible absorption strength (ε > 3 × 10 6 M(dot) −1 cm −1 ) and a high fluorescence quantum yield (73%). The high homogeneity of these dots reflects in many domains: morphological (narrow size distribution), structural (quasiperfect nanocrystals with large electronic bandgaps), and optical (nontunable fluorescence from a single electronic transition). Moreover, we provide the proof of principle that an aqueous solution of these dots can be used as an active medium in a laser cavity, displaying a very efficient laser emission with dye-like characteristics, which reflects the benefits of such a highly homogeneous type of carbon-based nanodots.

We report an experimental investigation by Raman spectroscopy of the decomposition process of Metal-Organic Framework (MOF) HKUST-1 upon exposure to air moisture (T=300 K, 70% relative humidity). The data collected here are compared with the indications obtained from a model of the process of decomposition of this material proposed in literature. In agreement with that model, the reported Raman measurements indicate that for exposure times longer than 20 days relevant irreversible processes take place, which are related to the occurrence of the hydrolysis of Cu-O bonds. These processes induce small but detectable variations of the peak positions and intensities of the main Raman bands of the material, which can be related to Cu-Cu, Cu-O, and O-C-O stretching modes. The critical analyses of these changes have permitted us to obtain a more detailed description of the process of decomposition taking place in HKUST-1 upon interaction with moisture. Furthermore, the reported Raman data give further strong support to the recently proposed model of decomposition of HKUST-1, contributing significantly to the development of a complete picture of the properties of this considerable deleterious effect.

The local environment of iron in FeBTC, a metal organic framework commercially known as Basolite F300, is investigated combining XANES and EXAFS studies of the iron Kedge. The building block of the FeBTC can be described as an iron acetate moiety. Dehydration induces a change in the coordination of the first shell while preserving the network. We propose that the local structure around Fe atoms does not undergo a rearrangement, thus leading to the formation of an open site. The analysis conveys that the FeBTC is a disordered network of locally ordered blocks.

We report on nitrogen-doped carbon dots having a β-C3N4crystalline structure and yielding bright tunable fluorescence.