The present invention relates to a process for preparing a porous material, at least comprising the steps of providing a mixture (I) comprising a composition (A) comprising components suitable to form an organic gel and a solvent (B), reacting the components in the composition (A) in the presence of the solvent (B) to form a gel, and drying of the gel obtained in step b), wherein the composition (A) comprises a catalyst system (CS) at least comprising a catalyst component (C1) selected from the group consisting of ammonium salts and a carboxylic acid as catalyst component (C2). The invention further relates to the porous materials which can be obtained in this way and the use of the porous materials as thermal insulation material and in vacuum insulation panels and vacuum insulation systems, in particular in interior or exterior thermal insulation systems as well as for the insulation of refrigerators and freezers and in water tank or ice maker insulation systems.