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

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 FeIII metallacycle complex [Fe2(H2opba)2Cl2(dmso)2]·2CH2Cl2·2dmso (1) with excellent capacity to selectively adsorb ammonia (11.3 mmol...

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Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019-01, 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
Subjects:
Adsorbents
Adsorption
Amines
Ammonia
Crystallography
Energy
Flux density
Mass spectrometry
Mass spectroscopy
Nuclear fuels
Organic chemistry
Organometallic compounds
Selectivity
Storage
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Summary: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 FeIII metallacycle complex [Fe2(H2opba)2Cl2(dmso)2]·2CH2Cl2·2dmso (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.
ISSN:2050-7488
2050-7496
DOI:10.1039/c8ta09786k