Using porous boron nitride in adsorption-based processes: investigation of material challenges and opportunities

Abstract

In 2016, industrial separation processes accounted for 10-15% of the global energy consumption. This striking figure has urged the scientific community to continue developing new materials and technologies to significantly reduce global emissions in industry, for example in the field of adsorption processes. In light of this, porous boron nitride (BN) has gradually appeared as a promising adsorbent owing to its tunable chemistry and porosity, which a priori make it adaptable for various applications. However, research on porous BN remains at laboratory scale due to a lack of understanding of its formation mechanism. Furthermore, the material has displayed hydrolytic instability, which is an issue due to the presence of moisture in most industrial settings. Finally, the use of porous BN has mainly been focusing on molecular separations, but little is known about its potential for other adsorption-based applications, such as thermal energy storage. In this thesis, I first investigated the formation mechanism of porous BN to shed light on the critical steps of its synthesis. Considering a wide range of separations, I then searched new ways of enhancing its hydrolytic stability via surface functionalization. I developed two methods involving organosilane grafting, which produced porous BN adsorbents with enhanced moisture resistance and adequate CO2/N2 selectivity in the context of CO2 capture. Finally, I expanded the range of possible applications using porous BN and researched its potential for thermochemical energy storage, which has recently emerged as a key technology to mitigate CO2 emissions. I prepared BN-based adsorbents with various structural and thermal properties, allowing to understand how material properties affect the performance in thermochemical energy storage via adsorption. Overall, this thesis presents new knowledge on porous BN and explores the opportunities and challenges associated with its unique properties in the context of adsorption-based applications, in particular CO2/N2 separation and thermochemical energy storage.