(Ga1−xAlx)4B2O9: controlled surface acid–base properties and catalytic behavior towards the Strecker reaction

Abstract

Solid bases are valuable catalysts for industrial syntheses. However, controlling the basicity of these catalysts remains a challenge. Ga₄B₂O₉, due to μ₃-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_xGa_1−x)₄B₂O₉. According to the results of NH₃-TPD, CO₂-TPD, and the systematic experimental design, Lewis basic sites originating from GaO₅ groups in (Al_xGa_1−x)₄B₂O₉ 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.