Enhanced catalytic performance of transition metal-doped Co/TiO₂ for continuous-flow synthesis of borneol from...

Borneol, a pharmaceutically important monoterpenoid, has emerged as a key ingredient in modern medicinal formulations. Here, we report a highly efficient heterogeneous catalytic system using transition metal-doped Co/TiO₂ catalysts for the continuous-flow isomerization of isoborneol to borneol. Through systematic screening of bimetallic combinations, we demonstrate that Cu and Ni dopants synergistically enhance the redox properties of Co species, particularly improving hydrogenation-dehydrogenation efficiency in the isomerization of isoborneol. The optimized 1Cu-3Co/TiO₂ catalyst (Cu : Co = 1 : 3 mass ratio) enabled a two-stage continuous-flow system, achieving 58% molar yield of borneol with <0.4% camphor byproduct formation after solvent removal. Remarkably, the catalyst maintained >99% metal retention during a total of 200 h of continuous reaction. This work not only provides fundamental insights into promoter effects in bimetallic catalysis but also establishes a commercially viable platform for continuous production of high-purity botanical therapeutics.