Enhancement of solid base activity for porous boron nitride catalysts by controlling active structure using post treatment

Porous boron nitride (BN) was synthesized using a pyrolysis method in conjunction with varying NH₃ flow rates, followed by washing as a post-treatment. The performance of this material as a solid base catalyst was assessed. It was found that the post-treatment rather than the synthesis conditions significantly improved the activity of the BN during the nitroaldol reaction. The BN catalyst obtained after washing gave a ten times higher product yield. Both an increase in the surface areas of the material and the emergence of micropores after washing were observed. ¹¹B solid-state nuclear magnetic resonance spectroscopy demonstrated that boron oxide species were present in the BN after synthesis but were removed by the washing process. B K-edge X-ray absorption fine structure analyses indicated the formation of oxygen-substituted trigonal boron sites on the BN surface. Fourier transform infrared spectroscopy showed that amino groups on the samples functioned as moderately strong basic sites.