Interplay of Linker Functionalization and Hydrogen Adsorption in the Metal–Organic Framework MIL-101

Functionalization of metal–organic frameworks results in higher hydrogen uptakes owing to stronger hydrogen–host interactions. However, it has not been studied whether a given functional group acts on existing adsorption sites (linker or metal) or introduces new ones. In this work, the effect of two types of functional groups on MIL-101 (Cr) is analyzed. Thermal-desorption spectroscopy reveals that the −Br ligand increases the secondary building unit’s hydrogen affinity, while the −NH2 functional group introduces new hydrogen adsorption sites. In addition, a subsequent introduction of −Br and −NH2 ligands on the linker results in the highest hydrogen-store interaction energy on the cationic nodes. The latter is attributed to a push-and-pull effect of the linkers

Amino-grafted Cu and Sc Metal-Organic Frameworks involved in the green synthesis of 2-amino-4H-chromenes. Mechanistic understanding.

In this work, we report for the first time a new methodology for the eco-synthesis of 2-amino-4H-chromenes 1, from salycilaldehydes and cyano compounds, under solvent-free and mild conditions, using amino-grafted MOFs as catalysts. The selected MOFs − commercial CuBTC and MIL-100(Sc) previously synthetized in our laboratories − can be easily functionalyzed with amines of different nature showing notable differences in their composition and textural properties. The total or partial functionalization of the metal centers in starting MOFs is strongly depending on the functionalization method used. Our results indicate that the catalytic performance is mainly conditioned by the type and concentration of basic sites, porosity of the samples barely showing any influence. The methodology herein reported could be considered as an environmental friendly alternative to the selective chromene synthesis, which allows to achieve high yields in relatively short reaction times (up to 90% over 1 h), using notably small amounts of easily prepared catalysts. Furthermore, our experiments in combination with theoretical calculations strongly suggest that free-amine groups in ethylenediamine (EN) functionalized catalysts can act either as individual catalytic sites, as for ENM/ CuBTC sample, in which all metal centers are functionalized with EN ligands and shows the highest concentration of basic catalytic sites, or acting in cooperation with the closest metal centers in samples partially functionalized, as in the case of EN/CuBTC sample.pre-print1486 K

Quantum Chemical and FTIR Spectroscopic Studies on the Linkage Isomerism of Carbon Monoxide in Alkali-Metal-Exchanged Zeolites: A Review of Current Research

When adsorbed (at a low temperature) on alkali-metal-exchanged zeolites, CO forms both M(CO)+ and M(OC)+ carbonyl species with the extra-framework alkali-metal cation of the zeolite. Both quantum chemical and experimental results show that C-bondend adducts are characterized by a C−O stretching IR band at a frequency higher than that of 2143 cm-1 for free CO, while for O-bonded adducts this IR band appears below 2143 cm-1. The cation-CO interaction energy is higher for M(CO)+ than for M(OC)+ carbonyls, although the corresponding difference decreases substantially when going from Li+ to Cs+. By means of variable-temperature FTIR spectroscopy, this energy difference was determined for several alkali-metal cations, and the existence of a thermal equilibrium between M(CO)+ and M(OC)+ species was established. The current state of research in this field is reviewed here, with a view to gain more insight into the thermal isomerization process