A picolinamide iridium catalyst immobilized on an aluminum-hydride anchor for the selective dehydrogenation of neat formic acid

Abstract

The dehydrogenation of formic acid can provide an efficient pathway for hydrogen generation in the presence of a suitable catalyst. Homogeneous catalysts have been extensively studied and utilized for highly active and selective processes compared to conventional heterogeneous catalysis, which often shows lower reactivity and selectivity. However, the latter is preferred for practical applications, considering its easy separation and recyclability. By incorporating a homogeneous organometallic complex on an appropriate support, the unique features of both catalysts can be combined and utilized effectively. Herein, we investigate the immobilization of an iridium picolinamide complex (1) supported on 3D fibrous modified silica that demonstrates high accessibility. The support involves a tetracoordinate aluminum hydride site featuring a strong Lewis acidic nature. A study of the interaction and coordination sites around the surface fragment was conducted via various techniques, including elemental analysis, FT-IR, solid-state NMR, XAS, and first-principles calculations, which provided informative data. We explored the use of solid additives in a solvent-free reaction medium and avoided utilizing volatile bases to achieve process feasibility with a high TOF of 40 000 h⁻¹.