Novel Functionality of Organic 6,13-Pentacenequinone as a Photocatalyst for Hydrogen Production under Solar Light

6,13-Pentacenequinone (PQ), an intermediate for an organic semiconductor pentacene, was synthesized by single step solvent free solid state reaction at room temperature under ambient conditions which is hitherto unattempted. The phase purity has been confirmed by XRD and NMR. Optical study showed the absorption at 390 and 412 nm attributed to the π-π* and n-π* transitions, respectively. Cyclic voltammetry indicates the semiconducting nature of PQ having a band gap of 3 eV. The photoluminescence study revealed emissions at 408 and 432 nm. Considering the good thermal stability and absorption well within visible region, wisely, PQ has been used as a photocatalyst for the hydrogen production under solar light. Surprisingly we observed the utmost hydrogen evolution i.e. 4848 μmol/h/0.1 g (quantum efficiency 6.8%). The repeatability and reusability study confirmed the stability of the photocatalyst. The confirmation of the photocatalytic effect was also confirmed using methylene blue (MB) dye degradation under natural sunlight. The observed rate constant (Kapp) for photocatalytic MB degradation was 1.60 × 10(-2) min(-1). The use of an organic photocatalyst for hydrogen production has been demonstrated for the first time. This novel organic photocatalyst can also be explored for water splitting.