(Ga 1- x Al x ) 4 B 2 O 9 : controlled surface acid-base properties and catalytic behavior towards the Strecker reaction.

Solid bases are valuable catalysts for industrial syntheses. However, controlling the basicity of these catalysts remains a challenge. Ga 4 B 2 O 9 , due to μ 3 -O within its structure, could behave as a special solid base catalyst exhibiting intrinsic Lewis basicity. In this work, a sol-gel method was proposed to obtain continuously adjustable acidity and basicity of the metal borate catalyst (Al x Ga 1- x ) 4 B 2 O 9 . According to the results of NH 3 -TPD, CO 2 -TPD, and the systematic experimental design, Lewis basic sites originating from GaO 5 groups in (Al x Ga 1- x ) 4 B 2 O 9 boost the Strecker reaction rather than the Lewis acid sites related to unsaturated Al. This work illustrates the possible application of bulk-type solid solutions with simultaneous Lewis acid and base sites for the first time. A reaction mechanism has also been proposed based on the catalytic reaction results.