Deep eutectic solvent-modified mesoporous silica for CO2 capture: A new generation of hybrid sorbents

The escalating level of atmospheric carbon dioxide (CO2) is currently one of the most pressing environmental concerns for scientists. Consequently, a wide range of sorbents are investigating for their CO2 uptake ability. Studies showed that morphology-controlled mesoporous silica (MPS) and deep eutectic solvents (DESs) perform exceptionally well towards CO2 capture. However, based on their respective physicochemical properties, both MPS and DES systems have their own drawbacks when used separately. A novel strategy is adopted here by combining MPS and DES [choline chloride: ethylene glycol (ChCl: EG):: 1: 2 mol ratio] to prepare a hybrid high-performing porous sorbent - porous DES (PDES) for CO2 capture. PDES has shown superior CO2 capture capacity relative to the DES (ChCl: EG) alone. CO2 capture efficiency of PDES system was further improved by adding superbases 1,5-diazabicyclo[4.3.0]–non-5-ene (DBN). DBN-added PDES system exhibited remarkable CO2 uptake efficiency of 72.4 mg/g (mg of CO2 captured/g of liquid media) and excellent CO2 absorption-expulsion reversibility. The work establishes that a functional MPS-DES combination can enhance CO2 absorption dramatically creating a new generation of high-performing, inexpensive, environmentally-friendly, and widely accessible porous liquid material as effective CO2 sorbent.