Speaker
Description
Understanding the nanoscale dynamics of water molecules incorporated in layered and porous solids is key in designing next-generation materials for water filtration devices and fuel cells and requires the combination of experimental measurements and MD simulations. Cold neutrons, allowing investigations of molecular motions on a pico- to nano-seconds time regime, offer critical complementarity to computational modelling studies, where experimental parameters are used to feedback into model inputs, providing an effective methodology to understand properties of materials, as well as guiding advanced designs. We have previously demonstrated that crystalline carbon nitrides with a layered polytriazine imide (PTI) structure spontaneously absorbs ~9wt% of water from the atmosphere [1]. Here we present a comprehensive study combining QENS measurements with DFT and ab initio molecular dynamics calculations to describe and quantitative determine water transport throughout graphene-like materials.
Our data indicate that water travels as single-file through nanometer-sized voids ordered within the PTI layers. The process shows a permeance rate similar to subnanometres carbon nanotubes and graphene oxide assemblies. The transport mechanism involves sequence of orientation reversals directed by hydrogen bonding interactions with -N= and -NH groups decorating the ring voids within the carbon nitride nanosheets [2]. The latter resembles the selective transfer through Aquaporin channels in biological systems where water diffusion is facilitated by hydrogen bonding interactions between transported molecules and protein. The results suggest that these PTI-layered nanoporous materials represent excellent candidates for inclusion in membrane systems for next-generation energy and nanofiltration device applications.
References
[1] Suter T. et al. “Formation of an ion-free crystalline carbon nitride and its reversible intercalation with ionic species and molecular water” Chem. Sci., 2019, 10, 2519-2528.
[2] Foglia F. et al., “Aquaporin-like water transport in nanoporous crystalline layered carbon nitride” Sci. Adv., 2020, 6, 39.
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