The catalytic reduction of carbon dioxide to carbon monoxide under mild conditions using aromatic aldehydes as reductants and NHCs as organocatalysts was developed. This carbon dioxide splitting reaction provides a new method for metal-free carbon dioxide reduction and steps forward in utilizing carbon dioxide as a renewable "green" source under mild conditions. On the other hand, this reaction also shows a new economical way to oxidize aromatic aldehydes under mild conditions with carbon dioxide and could be applied in pharmaceutical synthesis.

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A mesoporous poly-melamine-formaldehyde polymer with a high surface area, good porosity and a high density of amine and triazine functional groups was investigated as a highly efficient hydrogen-bonding catalyst. This porous organic polymer was found to be highly effective in catalyzing chemoselective acetalization of aldehydes, without the consumption of any dehydrating agents. The turnover frequency of mesoporous poly-melamineformaldehyde is hundreds of times higher than melamine monomer, and this high efficiency is due to the high density of aminal (-NH-CH 2 -NH-) groups and triazine rings in the polymer network, which provides an inherently powerful system with multiple hydrogen bonds. This unique characteristic imparts mesoporous poly-melamine-formaldehyde polymer with a very high activity as a heterogeneous organocatalyst. The polymer is also low cost, and easy to be synthesized and recycled. † Electronic supplementary information (ESI) available. See

Gold(III) chloride catalyzed direct amination of arenes with azodicarboxylates was developed. The new catalytic system was active to a broad range of substrates, and the reaction was carried out under mild conditions. It represents the first catalytic system for the direct amination of electron-deficient arenes with azodicarboxylates to the best of our knowledge. This reaction provides an important approach for the synthesis of heterocyclic compounds in pharmaceutical and chemical industries.