An Fe dinuclear metallacycle complex as a size-selective adsorbent for nitrogenous compounds and a potentially effective ammonia storage material

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019-06, Vol.7 (25), p.15225-15232
• Main Authors: Silva, Ingrid F, Teixeira, Ivo F, Barros, Wdeson P, Pinheiro, Carlos B, Ardisson, José D, do Nascimento, Gustavo M, Pradie, Noriberto A, Teixeira, Ana Paula C, Stumpf, Humberto O
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta09786k

Ammonia has a large volume energy density and consequently high potential for application as a fuel and energy reservoir in the future. In this study, the dinuclear Fe III metallacycle complex [Fe 2 (H 2 opba) 2 Cl 2 (dmso) 2 ]·2CH 2 Cl 2 ·2dmso ( 1 ) with excellent capacity to selectively adsorb ammonia (11.3 mmol g −1 ) was investigated, demonstrating a strong preference for nitrogenous compounds, especially short-chain amines. The adsorption results suggest that the cavity in the structure of 1 has an essential role in the adsorption mechanism i.e. it is the responsible for size selectivity of 1 during the adsorption process. To better understand the adsorption mechanism of ammonia, 1 was fully characterized before and after adsorption. Thermogravimetric-mass spectrometry (TG-MS) and ammonia isotherm experiments revealed that 8 ammonia molecules were physisorbed by the complex cavity (free ammonia) and 4 ammonia molecules were chemisorbed (coordinated ammonia) per dinuclear metallacycle unit. Further characterization also confirmed the proposed adsorption mechanism, corroborating the structural modification of the compound after its interaction with ammonia; in addition, reuse tests showed that despite a small loss of efficiency, the compound was capable of desorbing most of the ammonia and could be used consecutively for at least three cycles. Thus, 1 is a potential ammonia storage material and adsorbent for the removal of ammonia from effluents. Study of the Fe III dinuclear metallacycle complex as a size selective adsorbent to amines with excellent capacity to adsorb ammonia.