Functionality dataset provides photocatalytic activity tests for NEPs, assessing the degradation of Nitrogen Oxide (NO) and nitrogen dioxide (NO₂) gases under visible light, measured via chemiluminescence. Key parameters recorded include irradiance (W/m²), temperature, and sample dimensions. NO degradation is quantified through initial NO concentration (ppbv) and exposure duration (min). TiO₂ deposition on PMMA substrates is quantified using ICP-OES, with measurements including TiO₂ mass (mg/m²), analysed area, PMMA weight (g/m²), sample weight and TiO₂ content per PMMA sample (mg). For textiles the TiO₂ concentration is expressed as mg Ti/g textile and wt%. This metadata includes measurements from 2 different partners, leading to apparent missing values due to differences in reporting metrics rather than actual data gaps