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Post-synthetic cation exchange in anionic metal–organic frameworks; a novel strategy for increasing the catalytic activity in solvent-free condensation reactions

Saeideh Beheshti, Ali Morsali
RSC advances 2014 v.4 no.79 pp. 41825-41830
benzaldehyde, catalysts, catalytic activity, cation exchange, cations, condensation reactions, coordination polymers, lithium, nickel, sodium, tetraethylammonium compounds
In recent years anionic MOFs (metal–organic frameworks) have only been scarcely explored for application in heterogeneous catalysis. In this work an anionic metal–organic framework, [HDMA]₂[Zn₂(BDC)₃(DMA)₂]·6DMF, has been prepared and its cations, HDMA⁺, were exchanged by Ni²⁺, Na⁺, Li⁺, tetraethylammonium (TEA⁺) and tetrapropylammonium (TPA⁺) by a post-synthetic process. By the strategy developed here, we have been able to prepare cation exchanged anionic MOFs as novel heterogeneous catalytic systems for solvent-free Knoevenagel condensation reaction between benzaldehyde and malononitrile. These catalysts were easily isolated from the reaction mixture and were reused several times without a significant degradation in activity.