Hydroxyl bond activation of formic acid by Metal-ligand cooperation of new designed aluminum ligated pincer fullerenes

Abstract

Abstract The two parts of the formic acid dehydrogenation reaction including catalyst activation and catalytic cycle with a new designed aluminum ligated NNN pincer fullerene as catalyst in which Al(III)– bis(imino)pyridyl pincer are located on the (6, 6) ring fusion bond of C60 fullerene was investigated with density functional calculations. Aluminum-ligand cooperation enables O-H bond cleavage of formic acid in the HCOOH-assisted H2 elimination pathway with protonation of imine carbon atom. The aluminum complex with three HCOO- units (complex 8) forms the active catalyst of HCOOH dehydrogenation. The existences of hydrogen bonds in the studied molecules were confirmed by NBO and AIM analyses. In the catalytic cycle, β-hydride elimination from 8 to dissociate CO2 and formation of Al–H complex promote HCOOH dehydrogenation to generate H2. The β-hydride elimination is the rate-determining step with an overall barrier of +17.8 kcalmol-1. The effect of fullerene cage on the catalytic cycle of HCOOH dehydrogenation is explored by elimination of fullerene cage from the Al(III)– bis(imino)pyridyl pincer fullerene.