期刊
MICROPOROUS AND MESOPOROUS MATERIALS
卷 225, 期 -, 页码 456-464出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.micromeso.2016.01.030
关键词
Metal-organic frameworks; CH4/N-2; Metal substitution; Selectivity; Adsorption behaviour
类别
资金
- HYPERLINK National Natural Science Foundation of China [21476231]
A series of isostructural ultra-microporous metal-organic framework (MOF) compounds [M-3(HCOO)(6)] (M = Mg, Mn, Co and Ni) have been readily synthesized in large-scale, characterized, and evaluated for the separation of CH4 and N-2. Results indicate that the metallic formates exhibit different CH4 adsorption capacities and distinct CH4/N-2 selectivity in a sequence of Ni > Co > Mg > Mn analogue owing to their varied CH4 affinities. Thereinto, [Ni-3(HCOO)(6)] shows the highest CH4 adsorption capacity of 1.09 mmol/g and CH4/N-2 selectivity up to 6.5 at 0.4 MPa and 298 K in the dynamic experiments, which suggests the most suitable synergistic effect between constricted pores and surface properties among [M-3(HCOO)(6)] frameworks. At the same time, the adsorption behaviour in [M-3(HCOO)(6)] is investigated by NH3-TPD, revealing that the adsorbed NH3 molecules should have two different states. One is that gas molecules stay inside the pores, the other is that gas molecules are adsorbed on the adsorption sites induced by the coordinated metal ions or exposed oxygen of the [M-3(HCOO)(6)], which directly affects the adsorption capacity, the ratio of two states of molecules and the final selectivity. These results confirm that alteration of metal ion plays an important role in the tuning of pore size and internal surface properties, thus providing new clues to design MOFs with different pore characteristics for enhanced gas sorption and separation. (C) 2016 Elsevier Inc. All rights reserved.
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