Densification and pelletization of porous boron nitride fibers for effective CO2 adsorption

Due to the rich pore structure and high specific surface area, porous boron nitride (BN) shows good performance in gas adsorption. Densification and pelletization of porous BN powder into pellets with high porosity, desired porous structure and good mechanical strength is highly required for its practical CO2 capture. Here, we demonstrate the high-yield synthesis of BN pellets via a dichloromethane-assisted precipitation, extrusion and pyrolysis process. Without using any polymer binders, porous BN fibers with high aspect ratios are crisscrossed with each other and assembled into BN pellets with uniform cylinder-shaped macroscopic morphology. After pelletization, the bulk density and mechanical strength of BN pellets have been effectively improved. The prepared BN pellets have high specific surface area of 1098.9 m2/g, and pore volume up to 0.47 cc/g, in which the micropore volume is as high as 93.6% of the total pore volume, thus making the pellets show excellent equilibrium and dynamic CO2 adsorption capacity. Especially, due to the extremely rich ulta-micropores, the CO2/N2 selectivity of BN pellets is calculated to be 20.6 (at 1 bar), higher than the previously reported BN adsorbents. The present work demonstrates a new idea for the pelletization of BN materials, which provides the possibility to further expand the application fields of BN materials.