Insights into porous material can improve sustainability of industrial processes

Understanding the formation of porous boron nitride will help reduce the energy required for large-scale processes such as carbon capture.

New research into the formation of a porous material known as porous boron nitride will help pave the way for improving large-scale industrial gas and liquid separations, such as those used in carbon capture or water treatment processes, by reducing the amount of energy required.

Porous adsorbent materials are important due to their large surface area, which makes them highly useful for a wide range of industrial applications. Adsorbents, as opposed to absorbents, are materials which allow a dissolved solid, liquid or gas to adhere to its surface.

One promising adsorbent is porous boron nitride, which makes an excellent candidate for successful separation processes due to its high porosity and thermal stability. However, most research remains at laboratory scale due to a lack of understanding of the formation mechanism of porous boron nitride which therefore prevents scale-up.

Research published in The Journal of Physical Chemistry C by the Petit Group, in collaboration with the University of St Andrews and Diamond Light Source, provides a greater understanding of how porous boron nitride forms and which can be used to scale-up separation processes.

Separations

Chemical separations account for between 10 and 15 per cent of global energy consumption, largely due to the many separation processes performed via distillation – the act of purifying a liquid by a process of heating and cooling.

Adsorbent materials which can separate molecules based on size and chemistry, have the potential to offer a less energy intensive, more sustainable route to separations.

However, to realise the potential of adsorption separation, scientists need to be able to produce porous materials with tailorable properties and porosities. 

Porous boron nitride

One candidate in the list of adsorption materials is porous boron nitride (BN) which, due to its high thermal stability and high surface area, has been tested for a range of applications including catalysis, carbon dioxide capture, oil spill clean-up, hydrogen storage and water cleaning. Understanding how porous BN is formed is crucial to enabling the scale-up of its synthesis and separation processes using it.

"We can now make greater predictions about the synthesis process of porous boron nitride and its adsorption properties at large scales. This will help pave the way for industrial processes to be carried out in a more sustainable way". Anouk L'Hermitte Department of Chemical Engineering

In their study, the team identified that a minimum temperature of 700 degrees Celsius is required to form porous BN. This temperature is key to ensuring that only boron nitride is obtained, rather than other intermediate molecules formed at lower temperatures. The researchers also observed the formation of non-porous carbon nitride prior to forming porous BN – a key step in the formation process which has not previously been mentioned in similar studies.

Lead author Anouk L'Hermitte said: “From our study we can now make greater predictions about the synthesis process of porous boron nitride and its adsorption properties at large scales. This will help pave the way for industrial processes to be carried out in a more sustainable way by reducing the amount of energy required.”

Next steps

The study only looked at one specific synthesis route, using specific reagents (the substances used to make the chemical reaction) and a maximum temperature of 1050 degrees Celsius. The next steps will therefore involve trialling the synthesis process in a larger set-up with a manufacturer and to test the obtained product for different separation scenarios.

Anouk L’Hermitte explained: “Our mechanistic study focuses on a given set of synthesis conditions. If one was going to use different reagents or a different temperature for example, the final porous boron nitride might be slightly different in terms of purity and porosity.”

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This work was carried out with the support of Diamond Light Source, instrument B07 (proposal SI-26588). The authors acknowledge the funding from bp-ICAM and the funding from the Engineering and Physical Sciences Research Council (EPSRC) through the CDT in Advanced Characterisation of Materials (2018 NPIF grant EP/S515085/1).

‘Formation Mechanism and Porosity Development in Porous Boron Nitride’ by L’Hermitte et al., published on 3 December 2021 in The Journal of Physical Chemistry C.

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