Tuning the Cerium-Based Metal-Organic Framework Formation by Template Effect and Precursor Selection.

The novel metal-organic framework [(CH)NH][Ce(bdc)(DMF)]·2HO (, Hbdc-terephthalic acid, DMF-,-dimethylformamide) was synthesized by a simple solvothermal method. has 3D connectivity of type with a dinuclear fragment connected with eight neighbors, while three types of guest species are residing in its pores: water, DMF, and dimethylammonium cations. Dimethylamine was demonstrated to have a decisive templating effect on the formation of , as its deliberate addition to the solvothermal reaction allows the reproducible synthesis of the new framework. Otherwise, the previously reported MOF Ce(bdc)(DMF) () or its composite with nano-CeO (CeO@) was obtained. Various Ce carboxylate precursors and synthetic conditions were explored to evidence the major stability of and within the Ce carboxylate-Hbdc-DMF system. The choice of precursor impacts the surface area of and thus its reactivity in an oxidative atmosphere. The PXRD and TG-DTA-MS study of in a nonoxidative atmosphere demonstrates that it eliminates HO and DMF along with (CH)NH guest species in two distinct stages at 70 and 250 °C, respectively, yielding [Ce(bdc)(Hbdc)]. The Hbdc molecule is removed at 350 °C with the formation of novel modification of Ce(bdc), which is stable at least up to 450 °C. According to the total X-ray scattering study with pair distribution function analysis, the most pronounced local structure transformation occurs upon departure of DMF and (CH)NH guest species, which is in line with the PXRD experiment. In an oxidative atmosphere, undergoes combustion to CeO at a temperature as low as 390 °C. MOF-derived CeO from , , and CeO@ exhibits catalytic activity in the CO oxidation reaction.