A novel
fluorinated biphenyldicarboxylate ligand of 3,3′,5,5′-tetrafluorobiphenyl-4,4′-dicarboxylic
acid (H2-TFBPDC) and its terbium metal–organic framework,
{[Tb2(TFBPDC)3(H2O)]·4.5DMF·0.5H2O}
n
(denoted as JXNU-6), were synthesized. JXNU-6 exhibits a three-dimensional
(3D) framework built from one-dimensional (1D) terbium carboxylate
helical chains bridged by TFBPDC2– linkers. The
3D framework of JXNU-6 features 1D fluorine-lined channels.
The gas adsorption experiments show that the activated JXNU-6 (JXNU-6a) displays distinct adsorption behavior for
propyne (C3H4) and propylene (C3H6) gases. The effective removal of a trace amount of C3H4 from C3H6 was achieved
by JXNU-6a under ambient conditions, which is demonstrated
by the column-breakthrough experiments. The modeling studies show
that the preferential binding sites for C3H4 are the exposed F atoms on the pore surface in 1D channels. The
strong C–H···F hydrogen bonds between C3H4 molecules and F atoms of TFBPDC2– ligands dominate the host–guest interactions, which mainly
account for the excellent C3H4/C3H6 separation performance of JXNU-6a. This
work provides a strategy for specific recognition toward C3H4 over C3H6 through the C–H···F
hydrogen bond associated with the fluorinated organic ligand.
The
novel sulfonate-carboxylate ligand of 5,7-disulfonate-1,4-naphthalenedicarboxylic
acid (H4-DSNPDC) was synthesized, and its series of lanthanide
compounds {[Ln3(μ2-OH)(DSNPDC)2(H2O)
x
]·yH2O}
n
(JXNU-7; Ln = La3+, x = 10. y = 4; Ln = Nd3+, Sm3+ Eu3+, x = 9, y = 2) and {[Ln4(μ3-OH)4(DSNPDC)2(H2O)11]·28H2O}
n
(JXNU-8; Ln = Eu3+, Gd3+) are presented. JXNU-7 is a three-dimensional structure based on linear trinuclear Ln3 building units, while JXNU-8 has a two-dimensional
layer constructed from tetranuclear Ln4(μ3-OH)4 building units. The representative Eu compounds
of JXNU-7 and -8 show good proton conductive
properties under high humidity. The hydrophilic sulfonate groups pointing
to the pores and the water molecules included in the pores mainly
contribute to the high proton conductivity for the materials. The
presence of one-dimensional infinite hydrogen-bonded networks in channels
of JXNU-7(Eu) facilitates a fast and efficient proton
transfer, resulting in higher proton conductivity in comparison to
that of JXNU-8(Eu). Additionally, JXNU-7(Eu) with a characteristic red emission exhibits a promising potential
for selective sensing of Fe3+ ions in aqueous solution.
Our work demonstrates the integration of functional organic components
(sulfonate groups) and inorganic components (lanthanide centers) in
MOFs for the successful preparation of multifunctional MOF materials.
The diphenylsulfone-3,3′-disulfo-4,4′-dicarboxylic acid (H 4 -DPSDSDC) ligand and its coordination polymers,were synthesized. The Zn(H 2 O) 4 units in 1 are connected by DPSDSDC 4− ligands to generate a one-dimensional (1D) chain, which is bridged by K−O bonds associated with bridging water molecules and sulfonate groups to yield a two-dimensional (2D) layer. In 2, the 1D hydroxyl-bridging Cu(II) chains are connected by DPSDSDC 4− ligands to give a 2D layer. The 2D layers in 1 and 2 are further connected by interlayered hydrogen bonds to give three-dimensional (3D) frameworks. Compounds 1 and 2 have good conductivities of 1.57 × 10 −4 and 5.32 × 10 −5 S cm −1 , respectively. Continuous well-defined hydrogen bonding networks associated with water molecules, sulfonate groups, and carboxylate groups were observed in compounds 1 and 2. Such hydrogen bonding networks provide hydrophilic domains and effective transfer pathways for protons. Here, we present elegant examples of a precise determination of the pathways for proton transport.
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