The investigation of an organic acid assisted sol–gel method for preparing monolithic zirconia aerogels

In our previous work, a citric acid assisted sol–gel method was developed for preparing monolithic metal oxide aerogels. Such method adopted citric acid as the gelator, which replaced the well-studied proton scavenger propylene oxide. In this work, we have further extended this “organic acid assisted” sol–gel method and investigated the gelation mechanism. Four different organic acids (butanedioic acid, l-malic acid, l-aspartic acid and mercaptosuccinic acid) with an identical main chain but different side groups were used as the gelators for preparing monolithic zirconia aerogels. It was found that complex interactions including covalent bond and coordination bond interactions between organic acids and zirconium ions were vital to give a rigid gel network. After supercritical drying, crystalline zirconia aerogels can be obtained with high surface areas over 330 m² g⁻¹ and large pore volumes over 3.574 cm³ g⁻¹.

The mechanism of the organic acid assisted sol–gel method free of propylene oxide for preparing monolithic zirconia aerogels was investigated in detail.