Facile Synthesis of Uniform Metal Carbide Nanoparticles from Metal-Organic Frameworks by Laser Metallurgy.

We report the fast and efficient conversion of metal-organic frameworks (MOFs) to phase pure transition-metal carbide (TMC) nanoparticles with uniform size using laser as the energy source, consuming only 6 W power. Nanoparticles of HfC, ZrC, TiC, V8C7, α-MoC, Cr3C2, and FeCx with homogeneous sizes (varied between 6 and 20 nm) were successfully produced, among which HfC and ZrC nanoparticles were obtained, for the first time, with sizes less than 10 nm and in the pure phase. This method was operated directly in air, in stark contrast to traditional furnace heating and laser spray methods, where a protective atmosphere is required. The use of MOFs allowed us to precisely tune the composition of TMC nanoparticles by dialing in the right type and desirable amounts of organic linkers. FeCx nanoparticles doped with various percentages of nitrogen atoms were synthesized for the Fischer-Tropsch reaction without any pretreatment or activation. Extremely high iron time of yield (FTY) values were observed, 415 and 550 µmol gFe-1 s-1 (with addition of K), in a 40 h test without any decay in performance. A high olefin to paraffin ratio was achieved for C2 to C11 products, where the ratio for C3 was higher than 10.