A Lewis acid-base paired InBO₃ catalyst: synthesis and high selectivity for isopropanol dehydrogenation

Whilst metal borates are well known as optical materials, their potential in solid catalysis has been less investigated. The calcite structured InBO₃ was selected as the target borate and was prepared using a solvothermal method. High-resolution transmission electron microscopy and powder X-ray diffraction prove that the material has a nanoparticle morphology with an average size ∼50 nm and high crystallinity. Intrinsic surface oxygen vacancies, which are beneficial to catalysis, were detected using X-ray photoelectron spectroscopy. Lewis acidity and basicity were both observed using NH₃-/CO₂-temperature-programmed desorption experiments, and the total acid and base amounts were found to be 46.6 and 123.8 μmol g^-1, respectively. Catalytic dehydration and dehydrogenation reactions for isopropanol at elevated temperatures were conducted in a fixed bed reactor to evaluate the catalytic performance of InBO₃. InBO₃ exhibits a high conversion rate (>90.5%) and, most importantly, a high dehydrogenation selectivity (acetone selectivity >92.5%), whilst the optimal acetone yield achieved was 121.3 mmol h^-1 g^-1_cat at 350 °C. This study on InBO₃ strongly suggests that metal borates have promising applications in heterogeneous catalysis.