This paper presents a study on CO2 capture by porous green concrete slab. CO2imprint has been steadily increasing in the world we live in especially due to industrial sector. Among the varied CO2 capture techniques, microalgae employment shows a better progress. This paper details about a construction-based CO2 sequestration technique, where a green lightweight slab with microalgae can be employed as a prefabricated compound wall to sequester CO2 from the atmosphere. It was found that porous geopolymer lightweight slab with microalgae had absorbed 30g of CO2for 20 sq.m than the slab without microalgae. It was also proved that about 27g of algal biomass has been imbibed on the porous slab with microalgae and 14 g on non-porous slab. Microalgae employed as green wall gives a luscious bright green aesthetic look. It is one of the most promising strategies for reducing the carbon dioxide footprint in the atmosphere using microalgae. Thus, using this technique, CO2sequestered can be a good way to reduce the global warming, thus illustrating the need for this study.