title: Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures.
abstract: Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.
authors: Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA.
authors: Yonggang
authors: Y
authors: Zhao
authors: Haohan
authors: H
authors: Wu
authors: Thomas J
authors: TJ
authors: Emge
authors: Qihan
authors: Q
authors: Gong
authors: Nour
authors: N
authors: Nijem
authors: Yves J
authors: YJ
authors: Chabal
authors: Lingzhu
authors: L
authors: Kong
authors: David C
authors: DC
authors: Langreth
authors: Hui
authors: H
authors: Liu
authors: Heping
authors: H
authors: Zeng
authors: Jing
authors: J
authors: Li
mesh_terms: D000327:Adsorption; D002245:Carbon Dioxide / Q000032:analysis / Q000493:pharmacokinetics*; D018360:Crystallography, X-Ray; D005740:Gases / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010795:Phthalic Acids / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D015032:Zinc / Q000737:chemistry*
chemical_list: D005740:Gases; D008024:Ligands; D009942:Organometallic Compounds; D010795:Phthalic Acids; D002245:Carbon Dioxide; C406866:2-hydroxyterephthalic acid; D015032:Zinc