A facile, sol−gel method to produce fluorescent, organically modified silica (ORMOSIL)−lanthanum phosphate (LaPO 4 ) hybrid nanocomposites suitable for gasphase CO 2 detection through a fluorescence-quenching mechanism is reported in the present work. ORMOSIL−LaPO 4 hybrid nanocomposites are prepared from a hybrid nanocomposite composition derived from trifunctional silanes such as methyltrimethoxysilane (MTMS), glycidoxypropyltrimethoxysilane (GPTMS), and from LaPO 4 nanorods, which act as fluorescent additives in the organically modified silane (ORMOSIL) matrix. Hybrid nanocomposite compositions containing MTMS and GPTMS were prepared in which the amount of LaPO 4 was varied. The wet alcogels thus obtained were dried under ambient conditions for 7 days, resulting in nanocomposite powders, and were calcined at 400 °C. The prepared nanocomposites were further characterized for their structural and functional features. The functional ORMOSIL matrix together with a luminescent additive like LaPO 4 makes the prepared ORMOSIL−LaPO 4 nanocomposite highly photoluminescent. The hybrid nanocomposite with nanoporous features exhibited a room-temperature CO 2 adsorption property and the photoluminescence intensity was found to quench with respect to CO 2 adsorption, which demonstrates the potential of the material to be used as a viable CO 2 sensor.