A highly active heterogeneous solid base catalyst has been synthesised from mesoporous silica and layered double hydroxide (LDH) nanocrystals by scientists in Shanghai, China.

Jianlin Shi and Liang Li have demonstrated for the first time that the pore channels of mesoporous silica (SBA-15) can be used as micro-reactors to in-situ synthesise layered double hydroxide nanocrystals. 

There are numerous methods for forming LDHs reported in the literature, with the challenge to synthesise smaller LDHs to improve their performance as catalysts. LDHs are layered materials with positively charged layers and charge balancing anions located in the interlayer region. 

Mesoporous materials, such as SBA-15, are an ideal support for catalysts, due to the well-designed and large open pore networks and good thermal and chemical stabilities. 

Shi has shown that using the mesoporous SBA-15 as a support, the pore channels act like micro-reactors, which are able to confine the growth of LDHs crystallites within the pore network. The resulting SBA-LDH material showed excellent catalytic activity towards aldol condensation reactions. This is due to the higher number of active edge sites on the SBA-15 support. 

'Many catalysts and guests can [now] be immobilized in the pore channels to get more active catalysts or other special composite materials' said Shi. The future challenge for this work is to be able to effectively load, control the structure and dispersion within the pore channels and recycle the guest catalysts without losing activity.

Emma Shiells