Two simple chemosensors with urea (L1) and thiourea (L2) groups were synthesized and studied by different spectroscopic techniques. Both receptors can sense acetate (Ac – ), dihydrogen phosphate (H 2 PO 4 – ), and fluoride (F – ) anions, accompanied by changes in UV–vis and 1 H NMR spectra, and an optical response is observed as a color change of the solutions due to deprotonation and hydrogen-bonding processes. Also, L1 and L2 were supported on TentaGel resins (R1 and R2), and their fluoride-sensing properties in DMSO and water solutions were studied. Interestingly, R2 can sense fluoride ions in sample solutions of 100% water.