Ratiometric fluorescence detection of melamine in milk by a zirconium-based metal-organic frameworks composite

•The ratiometric fluorescent approach of sensing melamine was successfully established.•The UiO-66-NH2@Ru nanocomposite was fabricated by a “one-pot” process.•UiO-66-NH2@Ru was applied to detect melamine in milk powder sample with good performance.•UiO-66-NH2@Ru is the first example of MOFs as a fluorescent “on–off” probe toward melamine.