Photoinduced manipulation of the nanoscale molecular structure and organization of soft materials can drive changes in the macroscale properties. Here we demonstrate the first example of a light-induced one- to three-dimensional mesophase transition at room temperature in lyotropic liquid crystals constructed from arylazopyrazole photosurfactants in water. We exploit this characteristic to use light to selectively control the rate of gas (CO2) diffusion across a prototype lyotropic liquid crystal membrane. Such control of phase organization, dimensionality, and permeability unlocks the potential for stimuli-responsive analogues in technologies for controlled delivery.