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.