Porous aluminosilicate geopolymers having a desired molar ratio of silicon dioxide to aluminum oxide are prepared by mixing an aluminosilicate powder in an alkaline silicate solution, placing into a sealed container, and then curing. The desired density and compressive strength of the geopolymer are achieved by varying the excess of alkaline silicate and by varying the curing temperature. The desired pore size distribution of the geopolymer is achieved by varying the curing conditions.