The porous composite BN@SHS made of boron nitride, silica hollow spheres and Si-O-B interface

Calcined silica SiO2 hollow spheres (SHS), with a specific surface area of 523 m(2) g(-1), were used as porous scaffolds of ammonia borane (AB). AB is used as precursor of boron nitride BN. By capillary effect, AB was infiltrated into the porosity of the SHS, and the as-obtained composite AB@SHS was pyrolyzed. Up to 160 degrees C, AB transforms into polyborazylene (PB); as a result, the composite PB@SHS was produced. Up to 600 degrees C, BN forms, and the composite BN@SHS was produced. Both composites are porous, with a specific surface area of 360 and 296 m(2) g(-1) respectively. Results from MAS NMR and XPS analyses showed that PB@SHS and BN@SHS contain B-O bonds, with more B-O bonds and possibly Si-O-B bonds for the latter. In other words, PB@SHS is made of PB, B-O bonds, and SiO2, while BN@SHS is made of BN, B-O bonds, possibly a Si-O-B interface, and SiO2. Based on first attempts, BN@SHS appeared to have a potential for improving the CO2 adsorption properties of the calcined SHS. Expressed in cm(3)(CO2) g(-1), the CO2 uptakes are 6.7 for BN@SHS and 6.3 for the calcined SHS, at 30 degrees C under 1.5 bar CO2; but expressed in mm(3)(CO2) m(-2), the respective CO2 uptakes are 22.6 and 12.

Automated summary

Calcined silica hollow spheres were used as porous scaffolds for the composite materials of ammonia borane and silica. Through pyrolysis, ammonia borane was transformed into polyborazylene and boron nitride, resulting in porous composite materials. The composite PB@SHS contains polyborazylene and B-O bonds, while BN@SHS contains boron nitride, B-O bonds, and possibly a Si-O-B interface and silica. Preliminary results showed that BN@SHS has the potential to improve the CO2 adsorption properties of the calcined silica hollow spheres.