A titania-coated honeycomb catalyst matrix is provided for the ultraviolet-photocatalytic oxidation of organic pollutants in a flowing fluid. A honeycomb-shaped skeletal structure (12) has a thin, lightweight substrate (18) of metal or ceramic, typically an aluminum alloy, and a surface coating (20) of photocatalyst, such as titania. The photocatalyst (20) is bonded to the substrate (18) via a thin oxide layer (18′) on the substrate. The oxide layer (18′) may be grown on the substrate. The photocatalyst coating (20) is made by mixing (30) titania powder in a TiO2 sol-gel to form a titania slurry. The substrate with oxide layer is coated (30) with the titania slurry and then heat treated (31). The photocatalyst coating (20) is typically applied to substrate sheets (40, 60, 62) preformed for assembly into a honeycomb-shaped skeletal structure (12) having an array of parallel cells (46, 46′). The coated sheets (40) may have troughs (42) and crests (42), and be stacked (34) with intermediate parting sheets (48). Alternatively, the coated sheets (60, 62) may be notched (64) and interfitted in “eggcrate” fashion. The honeycomb-shaped structure (12) is housed in a frame (50), and one or more stabilizer members (52) fastened to the frame serve to limit displacement of the structure as may be caused by the flowing fluid (14).