Microalgal biofilms are surface-attached, structured microbial communities containing sessile cells, which are often more resistant to pollutants and this increased resistance has a considerable impact on the treatment of exhaust gas and wastewater. However, microalgal biofilm cultivation occupies too much land. Aiming to improve space utilization, a three-dimensional (3D) porous biofilm photobioreactor (bPBR) was proposed by 3D printing. Nanoscale organosilicon particles, doped into the porous frameworks, served as light scattering media to introduce light into the inner structure of porous bPBR. With the help of nanoscale organosilicon particles, light could emit from the surface of the porous frameworks and illuminate every point on the frameworks of 3D bPBR. The average light intensity emitted from the light-conducting frameworks was up to 32 μmol m−2 s−1. The lowest light intensity emitted from the surface of the framework was 17 μmol m−2 s−1, still higher than the light compensation point (10 μmol m−2 s−1) of the microalgal biofilm. By extending the light-conducting frameworks in 3D space, the attached area for microalgae cells per landing area improved 34.5-times in the porous bPBR. The maximum biomass yield of the porous biofilm PBR could reach up to 31.7 g m−2, increased by 82.2 % compared to that cultivated in the flat biofilm PBR. It shows that the 3D porous bPBR has great potential for microalgal bio-fixation of CO2.