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

Abstract

The present work shows study of the CO₂ capture by amidines DBN and PMDBD using ¹³C solid-state NMR and thermal techniques. The solid state ¹³C 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 °C.