text: No heterogeneous catalyst has been commercialized for asymmetric hydrogenation.
  The first asymmetric hydrogenation focused on palladium deposited on a silk support. Cinchona alkaloids have been used as chiral modifiers for enantioselectivity hydrogenation.
  An alternative technique and one that allows more control over the structural and electronic properties of active catalytic sites is the immobilization of catalysts that have been developed for homogeneous catalysis on a heterogeneous support.  Covalent bonding of the catalyst to a polymer or other solid support is perhaps most common, although immobilization of the catalyst may also be achieved by adsorption onto a surface, ion exchange, or even physical encapsulation.  One drawback of this approach is the potential for the proximity of the support to change the behaviour of the catalyst, lowering the enantioselectivity of the reaction.  To avoid this, the catalyst is often bound to the support by a long linker though cases are known where the proximity of the support can actually enhance the performance of the catalyst.
  The final approach involves the construction of MOFs that incorporate chiral reaction sites from a number of different components, potentially including chiral and achiral organic ligands, structural metal ions, catalytically active metal ions, and/or preassembled catalytically active organometallic cores.  One of these involved ruthenium-based catalysts.  As little as 0.005 mol% of such catalysts proved sufficient to achieve the asymmetric hydrogenation of aryl ketones, although the usual conditions featured 0.1 mol % of catalyst and resulted in an enantiomeric excess of 90.6–99.2%.
  <br />