Unravelling the water adsorption mechanism in hierarchical MOFs: insights from in situ positron annihilation lifetime studies


Unravelling the water adsorption mechanism in hierarchical MOFs: insights from in situ positron annihilation lifetime studies

Attallah, A. G.; Bon, V.; Maity, K.; Hirschmann, E.; Butterling, M.; Wagner, A.; Kaskel, S.

Atmospheric water harvesting with metal-organic frameworks (MOFs) is a new technology
providing clean, long-term water supply in arid areas. In situ positron annihilation lifetime
spectroscopy (PALS) is proposed as a valid methodology for mechanistic understanding of water
sorption in MOFs and the selection of prospective candidates for desired applications. DUT-67-Zr
and DUT-67-Hf frameworks are used as model systems for method validation because of their
hierarchical pore structure, high adsorption capacity and chemical stability. Both frameworks are
characterized using complementary techniques such as nitrogen (77 K) and water vapour (298 K)
physisorption, SEM, and PXRD. DUT-67-Zr and DUT-67-Hf are investigated by PALS upon
exposure to humidity for the first time, demonstrating the stepwise pore filling mechanism by
water molecules for both MOFs. In addition to exploring the potential of PALS as a tool for
probing MOFs during in situ water loading, this work offers perspectives on the design and use of
MOFs for water harvesting.

Keywords: MOFs; DUT-67; positron annihilation lifetime spectroscopy; sorption mechanism; water harvesting

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Publ.-Id: 37567