The present invention concerns a process for capturing organosiliceous complexes in the gaseous or liquid phase on a solid containing at least 80% by weight of alumina after calcining at 1000.degree. C. The alumina has a total pore volume of more than 30 ml/100 g, a fraction of the pore volume in pores with a diameter of 70 .ANG. or more of more than 10 ml/100 g and a specific surface area of more than 10 m.sup.2/g.