Room-temperature synthesis of Fe-BTC from layered iron hydroxides: the influence of precursor organisation

The conversion of layered metal hydroxides into a metal-organic framework is studied for the case of Fe-BTC (BTC = 1,3,5-benzenetricarboxylate). The synthesis occurs at room temperature as early as 5 min using a layered double hydroxide, green rust, as a precursor and yielding a product with high surface area. Monitoring of the Fe-BTC crystallisation kinetics as a function of the degree of crystallinity of the iron hydroxide reveals the dependence of MOF assembly on the presence of a layered structure in the precursor. Further insights into the evolution of the structure and Fe centers are provided by thermogravimetric analysis, infrared, Mossbauer and electron paramagnetic resonance spectroscopy. The obtained Fe-BTC exhibited a higher crystallinity and a higher content of accessible Lewis-acid sites compared to the commercial counterpart, which in turn resulted in a higher catalytic activity for Knoevenagel condensation.