A unique hydrothermal selective hydrogenation process is carried out effectively in a simple and friendly way without adding any precious metal catalysts and hydrogen gas from outside. The self-assembly of the hydrogenated product 3-(4-(pyridin-4-yl)piperidin-1-yl) benzoate (PYPDB) with the zinc ion produces a highly stable photoactive complex Zn(PYPDB)₂ displaying interesting long range electron transfer behavior in the conjugated ring system.