Ethyne-Reducing Metal–Organic Frameworks to Control Fabrications of Core/shell Nanoparticles as Catalysts

Abstract

An approach using cobalt metal-organic frameworks (Co-MOF) as precursors is established for the fabrication of cobalt nanoparticles in porous carbon shells (core/shell Co@C). Ethyne deposition is used for controlling the reduction of cobalt nanoclusters in the MOF and the spontaneous formation of the porous carbon shells. The metallic cobalt cores formed are up to 4-6 nm with the crystal phase varying between hexagonally-closepacked (hcp) and face-centre-packed (fcc). The porous carbon shells changes from amorphous to graphene with the ethyne deposition temperature increasing from 400 to 600 o C. The core/shell Co@C nanoparticles exhibit high catalytic activity in selectively converting syngas (CTY: 254.1-312.1 μmolCOꞏgCo-1 ꞏs-1) into hydrocarbons (4.0-5.2 gHCꞏg-cat-1 ꞏh-1) at 260 o C. As well as the crystal size and phase, the coordination numbers of the cobalt to oxygen and to other cobalt atoms on the surface of the cobalt nanoparticles, and the permeability of the porous carbon shell have been related to the catalytic performance in FTS reactions.

Cobalt catalysts on carbon-based materials for Fischer-Tropsch synthesis: a review

“…In another work, Zhang et al [196] studied the impact of the reducing atmosphere, reaction temperature and time, using the Co-MOF approach on the formation of Co particles, Cospecies reduction, and nucleation and crystal growth steps. The Co/C catalyst prepared in an atmosphere of 2% C2H2 in helium led to smaller Co particle size, and higher reduction degree in comparison with the Co/C catalyst prepared in pure helium.…”

Carbon-based catalysts for Fischer–Tropsch synthesis

“…6(d). [136][137][138][139][140][141][142][143] Kapteijn et al: developed Co@SiO 2 catalyst by a stepwise methodology of making use of a cobalt-containing MOFs as a hard template: 144 The first step is the impregnation and hydrolysis of TEOS molecules in the pores of ZIF-67: The second step is the pyrolysis of ZIF-67@SiO 2 in N 2 resulting in the Co@C-SiO 2 catalyst. The final step is the calcination of Co@C-SiO 2 in the air to remove carbon: This preparation method results in well-dispersed cobalt nanoparticles with sizes of 5-15 nm: The cobalt loading was as high as B50 wt% with cobalt oxide reducibility of the order of 80%: Most importantly, the obtained Co@SiO 2 catalyst showed higher activity than the traditional impregnated Co/SiO 2 counterpart ( Fig.…”

“…In order to overcome these drawbacks of MOF-derived cobalt-based catalysts, Li's group developed a new preparation approach for the MOF-derived Co@C catalysts. 139 Co-MOF are established for the fabrication of cobalt nanoparticles in porous carbon shells and chemical vapor deposition (CVD) of ethyne over MOFs is utilized for the manufacture of ultrasmall cobalt species. The cobalt nanoparticles in the Co-MOF when were then reduced by the hydrogen released from ethyne during pyrolysis (Fig.…”

Engineering of Yolk/Core–Shell Structured Nanoreactors for Thermal Hydrogenations

“…The porous carbon shells derived from MOFs have been used for encapsulating metal NPs. [ 63 ] A ZIF‐67@am‐TiO 2 precursor was prepared and then pyrolyzed under nitrogen to form the Co@C core, then the carbon shell was removed by calcination under oxygen to form well dispersed Co 3 O 4 core with TiO 2 as shell. [ 64 ] Recently, the boron carbon nitride nanosheets (BCNNSs) were designed to encapsulate nano‐iron particles ( Figure a).…”