Efficient capture and storage of ammonia in robust aluminium-based metal-organic frameworks

The development of stable sorbent materials to deliver reversible adsorption of ammonia (NH3) is a challenging task. Here, we report the efficient capture and storage of NH3 in a series of robust microporous aluminium-based metal-organic framework materials, namely MIL-160, CAU-10-H, Al-fum, and MIL-53(Al). In particular, MIL-160 shows high uptakes of NH3 of 4.8 and 12.8 mmol g(-1) at both low and high pressure (0.001 and 1.0 bar, respectively) at 298 K. The combination of in situ neutron powder diffraction, synchrotron infrared micro-spectroscopy and solid-state nuclear magnetic resonance spectroscopy reveals the preferred adsorption domains of NH3 molecules in MIL-160, with H/D site-exchange between the host and guest and an unusual distortion of the local structure of [AlO6] moieties being observed. Dynamic breakthrough experiments confirm the excellent ability of MIL-160 to capture of NH3 with a dynamic uptake of 4.2 mmol g(-1) at 1000 ppm. The combination of high porosity, pore aperture size and multiple binding sites promotes the significant binding affinity and capacity for NH3, which makes it a promising candidate for practical applications. Porous sorbents capable of high ammonia (NH3) uptake capacities are of great interest for ammonia storage for industry, as well as for the environmental remediation of this toxic and corrosive gas. Here, NH3 adsorption is investigated in four robust aluminium-based metal-organic frameworks, and in situ neutron powder diffraction, synchrotron IR micro-spectroscopy and Al-27 solid-state NMR studies show that the pore geometries, framework rigidity, and nature of the host-guest binding sites together dictate the high NH3 capture and storage capacity.

Automated summary

The development of stable sorbent materials for reversible adsorption of ammonia is challenging. In this study, the efficient capture and storage of ammonia in four robust aluminium-based metal-organic frameworks were investigated. The results showed that MIL-160 exhibited high ammonia uptake capacity, and the pore geometry, framework rigidity, and host-guest binding sites played a crucial role in determining the ammonia capture and storage capacity.