Dual-active-sites deep eutectic solvents based on imidazole and resorcinol for efficient capture of NH3

Ammonia (NH3) exhaust emission is not only a waste of chemical raw materials, but also harmful to the environment and human health. However, commercial methods scrubbing with water or acids face the challenges of high cost and waste disposal. Deep eutectic solvents (DESs) have attracted extensive attention due to their simple preparation process and low cost. In this work, we report an efficient and reversible dual-active-sites DES for NH3 capture. The NH3 absorption performance under different NH3 partial pressures and temperatures, reversibility, selectivity of NH3 to CO2 as well as physicochemical properties of imidazole/resorcinol (1:1) were studied in detail. The results display that binary DES imidazole/resorcinol (1:1) can absorb up to 0.238 g NH3 per g DES at 293.15 K and 0.1 MPa, which is much higher than most previously reported functional ionic liquids and DESs. Quantum chemistry calculations, NMR and FT-IR results suggest that the high absorption capacity stems from the intermolecular hydrogen bonding interaction between ammonia molecules and H-3 of imidazole and –OH of resorcinol. Consequently, reversible DES imidazole/resorcinol (1:1) shows promise for industrial NH3 absorption.