Mechanochemical Synthesis of Fluorine-Containing Co-Doped Zeolitic Imidazolate Frameworks for Producing Electrocatalysts

Abstract

Catalysts derived from pyrolysis of metal organic frameworks (MOFs) are promising candidates to replace expensive and scarce platinum-based electrocatalysts commonly used in polymer electrolyte membrane fuel cells. MOFs contain ordered connections between metal centers and organic ligands. They can be pyrolyzed into metal- and nitrogen-doped carbons, which show electrocatalytic activity toward the oxygen reduction reaction (ORR). Furthermore, metal-free heteroatom-doped carbons, such as N-F-Cs, are known for being active as well. Thus, a carbon material with Co-N-F doping could possibly be even more promising as ORR electrocatalyst. Herein, we report the mechanochemical synthesis of two polymorphs of a zeolitic imidazole framework, Co-doped zinc 2-trifluoromethyl-1H-imidazolate (Zn0.9Co0.1(CF3-Im)2). Time-resolved in situ X-ray diffraction studies of the mechanochemical formation revealed a direct conversion of starting materials to the products. Both polymorphs of Zn0.9Co0.1(CF3-Im)2 were pyrolyzed, yielding Co-N-F containing carbons, which are active toward electrochemical ORR.

Triboelectric behaviour of selected zeolitic-imidazolate frameworks: exploring chemical, morphological and topological influences

“…The mechanochemical synthesis of both the qtz and SOD phases was successfully conducted with [ZnCO 3 ] 2 [Zn(OH) 2 ] 3 ; the qtz phase employed methanol as the liquid assisted grinding solvent with NH 4 NO 3 , and the SOD phase employed DMF without the use of NH 4 NO 3 . 31 …”

“…The mechanochemical synthesis of both the qtz and SOD phases was successfully conducted with [ZnCO 3 ] 2 [Zn(OH) 2 ] 3 ; the qtz phase employed methanol as the liquid assisted grinding solvent with NH 4 NO 3 , and the SOD phase employed DMF without the use of NH 4 NO 3 . 31 In our work, we adapted the procedures from Arhangelskis and co-workers for non-ball milling mechanochemical methods. For the qtz-Zn(CF 3 Im) 2 synthesis, a solid mixture of reagents was ground in a mortar and pestle for 30 minutes to produce the MOF powder.…”

Metal–organic framework composites from a mechanochemical process

“…Since then, more and more MOFs have been reported via mechanochemical synthesis. [57][58][59][60][61][62][63][64][65] It should be noted that mechanochemical synthesis is not limited to single metal and single linker MOFs as mixed metal and mixed linker MOFs could also be synthesized. 66,67 Thorne et al successfully synthesized mixed metal and mixed linker ZIF-62 ([Zn(Im) 2−x (bIm) x ], where Im = imidazole, bIm = benzimidazole) via mechanochemical ball milling.…”