Mesoporous Multiproton Ionic Liquid Hybrid Adsorbents for Facilitating NH₃ Separation

Abstract

Ionic liquids (ILs), as promising candidates for ammonia (NH3) separation and recovery, have attracted extensive attention due to their extremely low pressures, high gas affinity, and adjustable structures. However, the development of new absorbents or adsorbents for highly efficient, fast, and reversible separation is still a great challenge. In this work, multiproton ILs (MPILs) by simultaneously introducing two or more −H, −OH, or −SO3H sites into the cations were designed to enhance NH3 uptake, and the MPIL N,N,N′,N′-tetrakis (2-hydroxyethyl)ethylenediamine trifluoromethane sulfonate ([EdteH6][TfO]2) with four −OH and two −H sites exhibited a superhigh capacity of 5.08 mol NH3·(mol IL)−1 at 40 °C and 1 bar. To solve the slow gas–liquid mass transfer due to the high viscosity of MPILs, the designed MPILs were highly dispersed onto the molecular sieve HZSM-5 with abundant pore structures to prepare a series of porous MPIL-based hybrid adsorbents for NH3 adsorption. The highest capacity of 140.42 mg NH3·(g adsorbent)−1 at 30 °C and 1 bar was achieved by 60 wt % [EdteH6][TfO]2@HZSM-5-60 (HZ60) due to multiple hydrogen bonding and mesopore effects, which is superior to all of the nonmetal IL-based adsorbents reported to date. Meanwhile, the 60 wt % [EdteH6][TfO]2@HZ60 also exhibited high NH3/CO2 and NH3/N2 selectivities, which are almost 16 and 14 times greater than that of pure HZ60, respectively, along with excellent reversibility. This work provides a feasible way to design novel porous IL-based adsorbents for gas separation and recovery.

Phenoxy-Nitrile Bifunctional Ionic Liquid for Efficient Electroreduction of CO2 to Oxalate

“…Herein, a CO 2 absorption experiment was conducted to evaluate the CO 2 capacity in IL electrolytes. The experimental methods and apparatus were based on our previous work. , In a typical experiment, a certain mass of 5.0 g of phenoxy-nitrile bifunctional IL [TBP]­[p-CN-PhO] was weighed and placed into the customized absorption flask in a constant temperature water bath. Then, a CO 2 flow rate of 200 mL·min –1 was introduced into the flask.…”

Advanced Materials for NH3 Capture: Interaction Sites and Transport Pathways

“…The results showed that 20 wt% [2-Mim][NTf 2 ]@AC-980 exhibited a higher NH 3 adsorption capacity of 68.61 mg g −1 NH 3 at 303.15 K and 0.10 MPa (30% higher than that of pure AC) and excellent recyclability, benefiting from the synergistic interaction of hydrogen bonding between the ILs and NH 3 and hierarchical pores. To further improve the NH 3 adsorption performance, various task-specific ILs with multiple hydrogen-bond interaction sites/complexation sites and porous supports with different pore sizes were utilized to develop a variety of SILP materials, such as multiphoton ILs@HZSM-5 [ 152 ], hydroxyl ammonium protic ILs@MCM-41 [ 153 ], Zn-based ILs@FDU-12 [ 154 ], and MILs [Bmim] 2 [Co(NCS) 4 ]@silica composites [ 155 ]. Enhanced NH 3 adsorption capacity and excellent adsorption–desorption performance were achieved in these materials, presenting great potential for application.…”

Ionic liquids and deep eutectic solvents for NH3 absorption and separation: a review

“…The synergistic effect between the two has led to an exceptionally high uptake at high temperatures (15.2 mmol g −1 at 80.0 °C and 1.0 bar) and low NH 3 concentration (5.0 mmol g −1 at 25.0 °C and 10 000 ppm). Similarly, Zhang et al 99 designed, synthesized, and supported four novel hydroxyl-submitted ammonium protic ILs (HAPILs) with multiple hydrogen bonding sites for NH 3 onto porous molecular sieves with large surface area and great stability. The thermodynamic and kinetic properties of the obtained composites in the process of NH 3 adsorption were widely studied, and the adsorption mechanism was investigated by experiments and density functional theory (DFT) calculations.…”