A Fluorinated Metal‐Organic Framework, FMOF‐2, for Preferential Adsorption of Ethane over Ethylene

Abstract

The preferential adsorption of ethane over ethylene would significantly simplify the overall ethane-ethylene separation scheme for ethylene purification. Ethane-selective adsorbents are still lacking compared to ethylene-selective adsorbents. We discovered that a fluorinated Metal-Organic Framework, FMOF-2, exhibits preferential adsorption of ethane over ethylene at pressures in the range of 40 kPa with ideal adsorbed solution theory selectivity of 3.3. The material was characterized by X-ray diffraction, argon physisorption at 87 K, thermal gravimetric analysis, scanning electron microscope (SEM) image, and Xray photoelectron analysis. Exposed fluorine functional groups on a porous material produced via a hydrogen-bonding type electrostatic attraction are thought to serve as ethane adsorption sites.

Fluorinated metal–organic frameworks for gas separation

“…4 Timeline of trifluoromethyl-containing substituents used in gas separation. 2004: [Cu(hfipbb)(H 2 hfipbb) 0.5 ]: 4,4 0 -(hexafluoroisopropylidene)bisbenzoic acid (HFIPBB), 132 2006: [M(hfipbb)L x ]: M: Co, Cu, or Zn, L: 4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) (H 2 hfipbb), 65 2007: FMOF-1: 3,5-bis(trifluoromethyl)-1,2,4-triazolate (bftZ), 133 2009: [Zn 2 (L1)(py-CF 3 ) 2 ] n : trifluoromethyl (CF 3 ), 134 2011: [Cd 2 L(H 2 O)] 2 Á5H 2 O: Cd(NO 3 ) 2 Á6H 2 O: 4,4 0 -(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 135 2013: Tb-FTZB-MOF: 2-fluoro-4-(1H-tetrazol-5-yl)benzoic acid (H 2 FTZB), 118 [M 2 (hfipbb) 2 (ted)]: 4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) (HFPBBA), 136 2015: USTC-253-TFA: trifluoroacetic acid (TFA), 137 2016: (1) and ( 2) DUT-67-Tfa and DUT-67-Tfmba, [Zr 6 O 6 (OH) 2 (tdc) 4 (RCOO) 2 ]: RCOO À : trifluoroacetic acid (Tfa) and 4-(trifluoromethyl)benzoic acid (Tfmba), 120 2018: (1) [Zn(hfipbb)(bpt)] n Án(DMF) 2 Án(H 2 O), 4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) (HFPBBA), 138 (2) sql-1-CoNCSÁ2TFT: a,a,a-trifluorotoluene (TFT); 139 2019: (1) CFA-15, Cu II 3 (tfpc) 2 (OH) 2 ÁDMF: 3,5-bis(trifluoromethyl)-1H-pyrazole-4-carboxylic acid (H 2 -tfpc), 140 (2) MOF-808, MOF-TFA: trifluoroacetic acid (TFA); 68 2021: (1) [Cu 2 (HFPBBA) 2 (DMA) 1.42 (H 2 O) 0.58 ] n Á5.5nDMAÁ11.5nH 2 O: 4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) (H 2 HFPBBA), 141 (2) {[Cd(bpee) (hfbba)]ÁEtOH} n : (4,4 0 -(hexafluoroisopropylidene)bis(benzoic acid) (hfbba), 42 (3) FMOF-2: 2,2-bis(4-carboxyphenyl)hexafluoropropane (HFA), 142 (4) MAF-2F: 3-ethyl-5-trifluoromethyl-1,2,4-triazole (Hfetz), 66 (5) MAF-9: 3-ethyl-5-trifluoromethyl-1,2,4-triazole (Hfetz), 66 (6) UiO-66-(CF 3 ) 2 : 2,5-bis(trifluoromethyl)terephthalic acid (H 2 BDC-(CF 3 ) 2 ). 143 This journal is © The Royal Society of Chemistry 2022 Two regioisomers of Zr-based UiO-67 MOFs were obtained using the solvothermal method (UiO-67-ortho-2CF 3 : ZrCl 4 and 3,3 0 -bis(trifluoromethyl)-4,4 0 -biphenyldicarboxylic acid (H 2 BPDCo-2CF 3 ), and UiO-67-meta-2CF 3 :2,2 0 -bis(trifluoromethyl)-4,4 0biphenyldicarboxylic acid (H 2 BPDC-m-2CF 3 )) where the CF 3 group is introduced into the ligands.…”

Zn(II)–Siloxane Clusters as Versatile Building Blocks for Carboxylate-Based Metal–Organic Frameworks

“…Hydrophobicity is often considered as a key property of MOFs for the separation of particular gases, volatile organic chemicals, and biphasic liquids, as well as for improving material stability under humid conditions . Typical methods for enhancing the hydrophobicity of MOFs are post-synthetic treatments or ligand functionalization unless the framework is based on highly extended aromatic backbones. − The SiMOFs reported here suggest another and more convenient way of creating hydrophobic and highly porous solids without relying on post-synthetic or ligand modifications . It would even be possible to modulate the hydrophobicity simply by choosing a Si precursor with different substituents.…”

Solvent-Driven Dynamics: Crafting Tailored Transformations of Cu(II)-Based MOFs

“…Metal–organic frameworks (MOFs), comprising periodic arrangements of metal ions and organic linkers, have garnered significant attention as a subset of well-defined crystalline coordination polymers possessing intrinsic porosity. The pore size and its chemical environment can be precisely tailored to satisfy the specific requirements of diverse applications, such as catalysis, − gas storage and separation, − among others. − However, the interpenetration of frameworks has often been formed unexpectedly during the synthesis of desired MOFs. Depending on the topological nets constituting the framework, MOFs can be categorized by noninterpenetrated and interpenetrated classes, respectively, which are assembled with a single net in constructing the framework and two or more nets reinforcing each other and thereby filling micropore space with another net in building the framework. , Since the interpenetrated frameworks commonly with tiny pores and low internal surface area cannot be physically separated unless the framework is disassembled, MOFs have been rationally designed to prevent interpenetration .…”