CO2 Capture with Silylated Ethanolamines and Piperazines.

Invited for this month's cover is the group of Marcus Herbig from the TU Bergakademie in Freiberg. The cover picture shows the reaction of CO2 with a silyl derivative of the biogenic amine ethanolamine. The role of CO2 as a contributor to climate change makes "carbon capture" a desirable goal. However, in addition to simply capture CO2, aminosilanes form silylcarbamates, which represent starting materials for a variety of crucial chemicals. Thus, the entrapped CO2 represents a useful C1 building block. The ESF-funded Junior Research Group CO2-Sil at the TU Bergakademie Freiberg (represented by their Logo and location) pursues that kind of goals. CO2-Sil studies these key reactions of CO2 insertion in depth by syntheses, quantum chemical calculations and calorimetric experiments. CO2 brought to the ground by our method shall be feedstock for various branches in chemistry. Read the full text of their Full Paper at 10.1002/open.201900269.

CO2 Capture with Silylated Ethanolamines and Piperazines.

Amine treatment is commonly used to capture CO2 from exhaust gases and from ambient air. The Si-N bond in aminosilanes is capable of reacting with CO2 more readily than amines. In the current study we have synthesized trimethylsilylated ethanolamines, diethanolamines and piperazines and investigated their reaction toward CO2. All products were characterized by 1H, 13C, and 29Si NMR, RAMAN spectroscopy as well as mass spectrometry. The product of a twofold CO2-insertion into bis-trimethylsilylated piperazine was analysed by single-crystal X-ray diffraction. Furthermore, quantum chemical calculations (DFT) were used to supplement the experimental results. Geometry optimizations and NBO calculations for each starting material were carried out at the B3LYP level with different basis sets. DFT calculations at the B3LYP, WB97XD and M062x level were conducted for geometry optimization and frequency calculations to examine the thermochemical data. The calculations were carried out both for the gas phase and in solvent environment. The calculated reaction enthalpies varied between -37 and -107 kJ mol-1, while experimental values around -100 kJ mol-1 were determined.