A comparative solid state C-13 NMR and thermal study of CO2 capture by amidines PMDBD and DBN

The present work shows study of the CO2 capture by amidines DBN and PMDBD using C-13 solid-state NMR and thermal techniques. The solid state C-13 NMR analyses demonstrate the formation of a single PMDBD-CO2 product which was assigned to stable bicarbonate. In the case of DBN, it is shown that two DBN-CO2 products are formed, which are suggested to be stable bicarbonate and unstable carbamate. The role of water in the DBN-CO2 capture as well as the stability of the products to environmental moisture was also investigated. The results suggest that the carbamate formation is favored in dry DBN, but in the presence of water it decompose to form bicarbonate. Thermal analysis shows a good gravimetric CO2 absorption of DBN. Release of CO2 was found to be almost quantitative from the PMDBDH+ bicarbonate about 110 degrees C.