Tb-substituted layered double hydroxides (Tb-LDHs) with NO3- in the interlayer were synthesized by a hydrothermal method and then used to capture and sense CO32- in aqueous solution. X-ray diffractometry confirmed that single-phase Tb-LDHs with Tb contents of 1-5 mol% were successfully synthesized. The NO3- ions of 5 mol% Tb-substituted LDH (Tb5LDH) were exchanged by CO32- ions in a Na2CO3 aqueous solution at pH = 11. The ion exchange for Tb5LDH was promoted with increasing the concentration of the Na2CO3 solution. Photoluminescence spectroscopy revealed that Tb5LDH with CO32- in the interlayer displayed an excitation wavelength of 229 nm and exhibited a green emission signal originating from the 4f(8) -> 4f(7) 5d(1) transition, D-5(4) -> F-7(J) (J = 3, 4, 5, 6), in the range of 400-700 nm. The intensity of the emission signal of the ion-exchanged Tb5LDH excited at 229 nm increased with increasing the content of CO32- in Tb5LDH. These results indicate that Tb5LDH was capable of capturing and sensing CO32- dissolved in water by irradiation with 229-nm light.