(453c) Porous Boron Nitride - Moving up the Scale for Use in Industrial Molecular Separations

Industrial separation processes account for 10-15% of global energy consumption¹. The energy cost of large-scale gas and liquid separation processes like distillation could be significantly reduced by moving towards adsorption processes, i.e. using porous materials to separate molecules based on size and/or chemistry. An example of an inorganic adsorbent is porous boron nitride (BN): this material exhibits high surface area, high porosity and benefits from greater oxidative and thermal stability than common carbonaceous adsorbents². In this work, we are exploring the potential of porous BN as an efficient and recyclable adsorbent for molecular separations at industrial scale.

Recently, our group developed a new method to produce porous BN with enhanced surface area, tuneable porosity³ and promising liquid and gas separations performance. To further advance the use of porous BN, we must investigate its chemical stability. In fact, preliminary tests in our group pointed to the instability of the material in presence of water⁴. Considering this aspect, we functionalised the surface of porous BN via silanisation to enhance hydrophobicity and resistance to moisture. The samples were characterised before and after functionalisation using FTIR, XRD, XPS, TGA and SEM. The changes in hydrophobicity were monitored using water vapour sorption and contact angle measurements. In addition, the porosity of the material was probed before and after exposure to moisture and liquid water with nitrogen sorption. The results point to the efficiency of the approach to produce moisture-resistant BN-based adsorbents.

In parallel, we also investigated the formation mechanism of porous BN via the comprehensive characterisation of intermediates at different synthesis temperatures using a combination of analytical and spectroscopic tools, including X-ray absorption spectroscopy. The results of this study not only provide valuable insight on how to tune better the porosity of the material, but also on how to improve the hydrolytic stability discussed above. Therefore, this research paves the way for scaling up the synthesis of porous BN towards industrial applications.

1. Sholl, D. S.; Lively, R. P., Seven chemical separations to change the world. Nature 2016, 532 (7600), 435-437.

2. Jiang, X.-F.; Weng, Q.; Wang, X.-B.; Li, X.; Zhang, J.; Golberg, D.; Bando, Y., Recent Progress on Fabrications and Applications of Boron Nitride Nanomaterials: A Review. Journal of Materials Science & Technology 2015, 31 (6), 589-598.

3. Marchesini, S.; McGilvery, C. M.; Bailey, J.; Petit, C., Template-Free Synthesis of Highly Porous Boron Nitride: Insights into Pore Network Design and Impact on Gas Sorption. ACS Nano 2017, 11 (10), 10003-10011.

4. Shankar, R.; Marchesini, S.; Petit, C., Enhanced Hydrolytic Stability of Porous Boron Nitride via the Control of Crystallinity, Porosity, and Chemical Composition. The Journal of Physical Chemistry C 2019, 123 (7), 4282-4290.