Ammonia adsorption by Al-MIL-53-TDC: performance evaluation and mechanistic study†

Ammonia is an important chemical raw material, and it is also a promising energy carrier or zero-carbon fuel. Given these multiple roles of ammonia, the separation and recovery of ammonia have become of utmost importance. Herein, a thiophene-based MOF Al-MIL-53-TDC was employed for ammonia adsorption. The ammonia capture capacity of Al-MIL-53-TDC is 12.6 mmol g⁻¹ at 1.0 bar and 25 °C. In a humid environment, the ammonia adsorption capacity is 2.95 mmol g⁻¹ under 25% ammonia solution. After several cycles of ammonia adsorption and desorption, the ammonia adsorption capacity can remain 71.6%. Results from FT-IR, XPS, and DFT calculations suggest that ammonia adsorption on Al-MIL-53-TDC primarily results from the interaction between the sulfur atom in the thiophene group and ammonia, as well as the hydrogen bonding interactions between the carboxylate group and ammonia.