Mechanically stable structured porous boron nitride with high volumetric adsorption capacity

The development of adsorbents into structured and robust forms remains a challenge for emerging porous materials. In the context of porous boron nitride (BN), studies point to a tradeoff between mechanical stability, porosity, density, and adsorption kinetics. Approaches towards shaping and densification of porous BN have been mostly empirical since a detailed understanding of its formation mechanism, and how it impacts mechanical strength and porosity, is lacking. Here, we demonstrate a synthesis method that can directly produce a mechanically robust structured BN from an easily scalable polymeric precursor, which results in the highest volumetric surface area among porous BN samples to date. Structured BN exhibits a high bulk density (ca. 0.3 cm(3) g(-1)), 50% higher than BN powders and over ten times higher than the structured BN aerogel, while maintaining fast sorption kinetics. Structured BN presents good mechanical strength, with hardness of 66.4 +/- 4.5 MPa determined via microindentation, i.e. one to two orders of magnitude higher than reported structured aerogels. Using a range of material characterisation techniques, we propose a formation mechanism for structured BN. This formation mechanism reveals that the crosslinked intermediates are responsible for the high mechanical strength of the final material. Our approach produces a form of BN that addresses the limitations of other BN- and non BN-based adsorbents, and facilitates their application in gas separation and storage technologies.

Automated summary

The research highlights the tradeoff between mechanical stability, porosity, density, and adsorption kinetics in porous boron nitride materials, and introduces a synthesis method for creating mechanically robust structured BN from a polymeric precursor. The structured BN demonstrates high bulk density, rapid adsorption kinetics, and good mechanical strength, with the formation mechanism revealing the importance of crosslinked intermediates in enhancing material strength.