Rational Construction and Performance Regulation of an In(III)–Tetraisophthalate Framework for One-Step Adsorption-Phase Purification of C₂H₄ from C₂ Hydrocarbons

Abstract

The development of porous materials for ethylene (C2H4) separation and purification, a very important separation process in the chemical industry, is urgently needed but quite challenging. In particular, the realization of selectivity-reversed adsorption (namely, C2H4 is not preferentially adsorbed) and the simultaneous capture of multinary coexisting impurities such as ethane (C2H6) and acetylene (C2H2) will significantly simplify process design and reduce energy and cost consumption, but such porous materials are quite difficult to design and have not yet been fully explored. In this work, by employing an aromatic-rich bithiophene-based tetraisophthalate ligand, we solvothermally fabricated an anionic In­(III)-based framework termed ZJNU-115 featuring In­(COO)4 as an inorganic secondary building unit as well as one-dimensional channels. Due to the absence of unsaturated metallic sites, together with aromatic-rich channel surface decorated with abundant hydrogen-bonding acceptors of carboxylate oxygen and thiophene sulfur atoms, desolvated ZJNU-115 exhibited an unusual adsorption relationship with respect to C2 hydrocarbons, namely, simultaneous and preferable capture of C2H6 and C2H2 over C2H4 at the temperatures investigated, thus representing a rare metal–organic framework (MOF) with the promising potential for one-step adsorption-phase purification of C2H4 from a trinary C2 hydrocarbon mixture. Compared to a few of the MOFs reported for such an application, ZJNU-115 displayed simultaneously good adsorption selectivities of both C2H2 and C2H6 over C2H4. Furthermore, its separation potential can be postsynthetically tailored by substituting dimethylammonium (Me2NH2 +) counterions with tetraalkyl ammonium ions (NR4 +; R = Me, Et, or n-Pr). More importantly, ZJNU-115 was stable in various organic solvents as well as aqueous solutions with pH values ranging from 5 to 9, thus laying a solid foundation for its practical applications. The design principle and the performance regulation strategy adopted in this work will offer valuable guidance for the contrapuntal construction of porous MOFs employed for direct multicomponent purification of C2H4 with improved performance.

A Microporous MOF Constructed by Cross-Linking Helical Chains for Efficient Purification of Natural Gas and Ethylene

“…At a gas-phase pressure of 109 kPa, the adsorption selectivity is 3.5 at 298 K, 3.7 at 288 K, and 3.9 at 278 K for a 1:99 C 2 H 2 −C 2 H 4 binary mixture. The values surpass or are comparable to those of some documented MOFs such as Dy-MOF (1.1), 54 ZJNU-14 (1.59), 55 ZJNU-7 (1.77), 56 ZJNU-115 (2.05), 57 FeMOF-74 (2.08), 29 Cu(TIA) (2.09), 58 NOTT-300 (2.17), 59 UPC-98 (3.1), 60 dia-[Sc(Hpzc)(pzc)] (3.1), 61 M′MOF-2 (3.12), 10 Mg-CUK-1 (3.13), 62 and NUC-19 (4.0). 63 As shown in Figure 3f, Since the pore dimension is larger than the kinetic diameters of the adsorbates considered in this work, different host−guest interactions should be responsible for preferentially adsorbing C 2 H n and CO 2 over CH 4 .…”

Synergistic binding sites in a hybrid ultramicroporous material for one-step ethylene purification from ternary C 2 hydrocarbon mixtures

“…Another important dimension is that the altering of anion pillars (e.g., SiF 6 ) can induce the distortion of pore shapes and the rotation of organic ligands (14,15), thus anionpillared HUMs have emerged as the promising C 2 light hydrocarbon adsorbents for binary separations such as C 2 H 2 /C 2 H 4 (16), C 2 H 2 / CO 2 (17), and C 2 H 4 /C 2 H 6 (18). However, the single-step C 2 H 4 purification from ternary C 2 mixtures has never been achieved in adsorptive separations using anion-pillared HUMs, because the quadrupole moment and kinetic diameter of C 2 H 4 [1.5 × 10 −26 (5,(20)(21)(22)(23)(24)(25)(26)(27).…”

Lanthanide–Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

“…For example, natural gas (NG) is composed mainly of methane (CH 4 ) but also includes various quantities of CO 2 as well as C 2 hydrocarbons. CO 2 /CH 4 and C 2 /C 1 separations thus present a major step toward NG purification, which avoids pipeline corrosion by acidic CO 2 and recovers C 2 hydrocarbon resources to increase its added values. − Apart from NG upgrading, C 2 H 4 purification is also a very important industrial process involving the capture from C 2 H 4 of its competing C 2 analogues, including acetylene (C 2 H 2 ) and ethane (C 2 H 6 ). − Due to their similar properties (Table S1), separation of C 2 H 4 from a trinary C 2 hydrocarbon mixture is extremely difficult. In addition, CO 2 as an impurity frequently exists in C 2 hydrocarbons.…”

“…In light of the HSAB (hard/soft acid/base) principle, upon coordination with trivalent lanthanide ions, the carboxylate groups serve as coordinating groups, while the pyridinic N atoms remain unbound as the potential sites for adsorbing C 2 H 2 and CO 2 molecules. Besides, the m- terphenyl skeleton favors the construction of a 3D coordination network, provides the resulting framework with rigidity and stability, and creates an aromatic-rich pore environment, a structural requirement considered for selective adsorption of C 2 H 6 in preference to C 2 H 4 . With the ligand at hand, we successfully fabricated a pair of isostructural LOFs via solvothermal reactions with Sm­(III) and Eu­(III) ions.…”

“…Besides, the m-terphenyl skeleton favors the construction of a 3D coordination network, provides the resulting framework with rigidity and stability, and creates an aromatic-rich pore environment, a structural requirement considered for selective adsorption of C 2 H 6 in preference to C 2 H 4 . 36 With the ligand at hand, we successfully fabricated a pair of isostructural LOFs via solvothermal reactions with Sm(III) and Eu(III) ions. Structural characterizations showed that they featured a 3D infinite metal−carboxylate SBU, which was rarely observed in the existing LOFs.…”