Low-Temperature\nDesorption of CO<sub>2</sub> from\nCarbamic Acid for CO<sub>2</sub> Condensation by Direct Air Capture

The high temperature\nrequirement for the desorption of\nabsorbed\nCO<sub>2</sub> is one of the issues for the widespread use of direct\nair capture (DAC), which is a promising technology to reduce atmospheric\nCO<sub>2</sub> concentration. This work realized a liquid diamine\nabsorbent–solid carbamic acid (CA) phase-change DAC system\nwith CO<sub>2</sub> desorption at a low temperature by using a MeOH\nsolvent. The CA of isophoronediamine [3-(aminomethyl)-3,5,5-trimethylcyclohexylamine,\nCA-IPDA] readily desorbed CO<sub>2</sub> in MeOH at 50 °C, while\nIPDA showed the capacity to absorb low-concentration CO<sub>2</sub> from air with an IPDA/CO<sub>2</sub> ratio of 1:1. The CA-IPDA desorbed\nmore than half of the absorbed CO<sub>2</sub> at 60 °C without\nany gas flow, proving that this system can condense low-concentration\nCO<sub>2</sub> in air to pure CO<sub>2</sub> with low energy requirements.\nThe low-temperature desorption of CO<sub>2</sub> from CA-IPDA was\nowing to the high solubility of CA-IPDA in MeOH and the easy CO<sub>2</sub> transfer between carbamic acid and MeOH to form methyl carbonate\nions. This solubility control in the liquid–solid phase-change\nsystem opens up the low-energy DAC systems.