Development of fast and intuitive detection techniques for explosive vapors is highly desired for security applications. Among those techniques, fluorescence quenching has advantages in terms of portability and maintenance cost compared to electrically driven platforms. One of the challenging issues is the restricted sensitivity (i.e., low initial quenching and quenching saturation) caused by hindered diffusion of gaseous analytes inside a dense, solid film, and resulting limited surface area, where the target molecules are reacting. Here, multilevel 3D porous nanostructures are introduced, which possess strong fluorescence and enhanced sensing abilities, produced by a rapid and scalable lithographic technique. The cyanostilbene fluorophore with low-absorption around patterning wavelengths (approximate to 355 nm) is newly designed to be incorporated into transparent photopolymer. The emission color and intensity of the composite films under excitation can be precisely controlled by adjusting the concentration of fluorophore based on intermolecular effects. The patterned, monolithic film with low-volume fraction (<40%) offers efficient diffusion paths inside a film and a large number of reaction sites for detecting gaseous analytes, enabling fast fluorescence quenching at an early stage (approximate to 7.5 times higher than the solid film at 30 s) and fully suppressed fluorescence without quenching saturation, which cannot be achieved by conventional solid films.