Fluorinated Biphenyldicarboxylate-Based Metal–Organic Framework Exhibiting Efficient Propyne/Propylene Separation

Abstract

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.

Metal‐Organic Framework Materials for Light Hydrocarbon Separation

“…adsorbent material to separate the C H 4 /C 3 H mixture is still in its infancy, and only a few publications have been reported so far. [26] Li et al conducted a study on the adsorptive separation of C 3 H 4 and C 3 H 6 by porous ELM-12, which is the first example for effectively separating C 3 H 6 /C 3 H 4 mixture. [27] ELM-12 shows very high C 3 H 4 /C 3 H 6 adsorptive selectivity and C 3 H 4 adsorption capacity in the low pressure environment.…”

“…Since the dynamic size of C 3 H 4 is particularly similar to that of C 3 H 6 , the separation is more challenging [25] . The use of MOF as the adsorbent material to separate the C 3 H 4 /C 3 H 6 mixture is still in its infancy, and only a few publications have been reported so far [26] …”

High Purity/Recovery Separation of Propylene from Propyne Using Anion Pillared Metal-Organic Framework: Application of Vacuum Swing Adsorption (VSA)

“…The ability to control their synthesis, functional surface groups, pore size offers the MOFs a great advantage in targeting specific difficult gas separations. Gases with a clear difference in molecular size, vapour pressures and other properties, such as CO 2 /N 2 , CO 2 /CH 4 , CO/CO 2 , O 2 /N 2 can be separated due to their different interaction with the MOF structure [8,10,12,19,45,46]. Gases with very similar molecular weights and vapor pressures (C 3 H 4 /C 3 H 6 /C 3 H 8 ) are very difficult to separate using traditional methods.…”

Crystal engineering of porous coordination networks for C3 hydrocarbon separation

“…For example, JXNU-6a was found to exhibit large C 3 H 4 uptake and efficient C 3 H 4 /C 3 H 6 separation performance due to C−H•••F hydrogen bonding interactions between the alkynyl hydrogen atoms of propyne molecules and the weakly basic fluorine atoms of fluorinated TFBPDC 2− ligands ( Figure 5B). 118 π-Complexing agents: Strong π-complexes are typically formed between some transition metal ions (e.g., Ag + , Cu + , Pt 2+ , and Pd 2+ ), and π-orbitals of unsaturated HCs. [144][145][146][147] Compared with sorbents containing common first-row transition metal (e.g., Cr, Mn, Fe, Co, Ni, Cu, and Zn), the former exhibit higher C 3 H 6 /C 3 H 8 selectivity.…”

“…ELM‐12 was found to exhibit high selectivity for C 3 H 4 over C 3 H 6 (84 for a 1:99 mixture), which was attributed to cavities that are shaped to form a better fit with C 3 H 4 than C 3 H 6 . Recently, a terbium PCN [Tb 2 (TFBPDC) 3 (H 2 O)] (JXNU‐6) with a novel fluorinated ligand was reported 118 to exhibit large C 3 H 4 uptake and modest C 3 H 4 /C 3 H 6 selectivity. The selectivity towards C 3 H 4 was attributed to C−H···F hydrogen bonds between propyne molecules and the F atoms of the linker ligands.…”