The porphyrin molecule has many roles in biological, chemical, and physical research, such as light absorbers in organic dyes for solar cells, due to its ease of modification.

Adel Ismail and Detlef Bahnemann, Central Metallurgical R&D Institute, Egypt, and Leibniz University, Germany, respectively, have used porphyrin-based meso-tetrakis(4-sulfonatophenyl) (TPPS) dye with mesoporous TiO₂ to form a metal-free 3D TPPS/TiO₂ film that is optically transparent and crack free.

The films were employed as a catalyst for the photodegradation of CH₃CHO in the gas phase. The photocatalyst was stable, could achieve a quantum efficiency of 0.059 % and could be recycled up to five times without loss in activity. These low-cost films could potentially be used for air purification and self-cleaning applications.

• Metal-Free Porphyrin-Sensitized Mesoporous Titania Films For Visible-Light Indoor Air Oxidation
  A. A. Ismail, D. W. Bahnemann,
  ChemSusChem 2010, 3, 1057–1062.
  DOI: 10.1002/cssc.201000158