Three-dimensional (3D) honeycomb-like structured graphene (HSG)-supported ternary K-promoted magnesium ferrite catalysts (K-MgFe/HSG) are prepared and evaluated in Fischer-Tropsch synthesis to the lower olefins (FTO). The catalysts bear interconnected mesoporous-macroporous framework of graphene nanosheets decorated with homogeneously sized magnesium ferrite nanoparticles (NPs). Under typical FTO reaction conditions, the composition-optimized 1K-MgFe/HSG catalyst affords a reduced CO2 selectivity of 40.4%, an excellent weight specific activity to hydrocarbons of 1825 mu mol(CO) g(Fe)(-1) s(-1), and an appreciable selectivity to the lower olefins (C-2 -C-4 olefins) of 57.8%, thus giving rise to a record high productivity of the lower olefins of 1055 mu mol(CO) g(Fe)(-1) s(-1) The excellent catalytic efficiency is tentatively attributed to the synergetic effect of Mg and K on adsorption and dissociation of CO. The catalyst also exhibits better durability than previously reported iron-based FTO catalysts, without significant changes in the catalytic performance and the size of the iron carbide NPs after 120 h on stream, highlighting the crucial role of the 3D porous HSG support in restricting the agglomeration of the active phase during the challenging high-temperature and exothermic FTO reaction. (C) 2019 Elsevier Inc. All rights reserved.