Mg2+ incorporated Co-based MOF precursors for hierarchical CNT-containing porous carbons with ORR activity

In this paper, we introduced light and abundant metal magnesium into a cobalt-based metal organic framework (Co-MOF, [(CH3)(2)NH2](2)[Co-3(bpdc)(4)]center dot 5DMF center dot 4CH(3)OH) (1, H(2)bpdc = 4,4'-biphenyldicarboxylic acid, DMF = N,N-dimethylformamide) as a heteroatom to synthesize Mg-Co bimetallic MOFs, namely [(CH3)(2)NH2](2)[MgCo2(bpdc)(4)]center dot 4DMF center dot 5CH(3)OH (2) and [(CH3)(2)NH2](2)[Mg1.2Co1.8(bpdc)(4)] 4DMF center dot 4CH(3)OH center dot 6H(2)O (3). Based on the formation of a rather low density framework after the introduction of the light Mg2+, such bimetallic MOFs exhibited higher gas adsorption abilities than the isostructural Co-based MOF 1. N-2 adsorption measurements demonstrate that the BET surface area of 3 is 305.4 m(2) g(-1), exhibiting three times that of 1 (104.4 m(2) g(-1)). Significantly, due to the introduction of the low-melting Mg2+, the Mg-Co MOFs could be further utilized as precursors for porous carbons only by calcination at a mild temperature of 600 degrees C which could exhibit a BET surface as high as 712.78 m(2) g(-1). Furthermore, after post-synthetic modification with a N/S heteroatom at 900 degrees C, the obtained hierarchical carbons exhibit superior activity in the oxygen reduction reaction (ORR) that is comparative to the commercial Pt/C catalyst. TEM results indicate that Co-embedded carbon nanotube (CNT)-containing hierarchically nanoporous carbons have been obtained. This study may offer a new avenue to prepare porous carbons utilizing Mg-containing bimetallic MOFs as sacrificial templates.