If a biomolecular chemical reaction is mass transport limited, the reaction rate can be accelerated by embedding one of the reaction centers in a molecular framework. This framework acts as a lower dimensionality surface along which the other reaction partner can travel. The rate enhancement can be identified with an increase in entropy of activation. A model for this effect is constructed and applied to a reaction center embedded in three molecular framework geometries: a linear chain, a disk, and a polar reactive patch on a sphere. The new result for the reactive patch on a sphere is relevant for enzymatic systems where substrates must find their way to a small reactive region.