GAS SEPARATIONS

Synergistic sorbent separation for one-step ethylenepurification from a four-component mixtureKai-Jie Chen1*†, David G. Madden2*‡, Soumya Mukherjee2, Tony Pham3§, Katherine A. Forrest3,Amrit Kumar2, Brian Space3, Jie Kong1, Qiu-Yu Zhang1, Michael J. Zaworotko2†

Purification of ethylene (C2H4), the largest-volume product of the chemical industry, currentlyinvolves energy-intensive processes such as chemisorption (CO2 removal), catalytic hydrogenation(C2H2 conversion), and cryogenic distillation (C2H6 separation). Although advanced physisorbent ormembrane separation could lower the energy input, one-step removal of multiple impurities, especiallytrace impurities, has not been feasible. We introduce a synergistic sorbent separation methodfor the one-step production of polymer-grade C2H4 from ternary (C2H2/C2H6/C2H4) or quaternary(CO2/C2H2/C2H6/C2H4) gas mixtures with a series of physisorbents in a packed-bed geometry. Wesynthesized ultraselective microporous metal-organic materials that were readily regenerated,including one that was selective for C2H6 over CO2, C2H2, and C2H4.

Purification of commodities currently con-sumes 15% of global energy, and com-modity demand has been projected totriple by 2050. Theproduction of ethylene(C2H4) and propylene (C3H6) uses 0.3% of

global energy production (1) as polymer-grade(>99.9% purity) C2H4 is produced by energy-intensive separation of downstream C2 hydro-carbon gas mixtures during the steam crackingprocess. Acetylene (C2H2) is removed throughcatalytic hydrogenation (with a noble-metalcatalyst at high temperature and pressure) orsolvent extraction (requiring a large volumeof solvent and a large plant installation).Removal of C2H6 occurs through cryogenicdistillation (2).The high energy footprint associated with

C2H4 production has spurred research intothe development of more energy-efficient ap-proaches to purification of these C2 gases. Toafford polymer-grade C2H4 in a single step,simultaneous removal of C2H2 and C2H6 fromC2H4 would be necessary. Chemical transforma-tion of C2H2 and C2H6 to C2H4, chemisorption,extraction, and membrane-based technologiescould in principle address the need, but eachapproach has drawbacks. The simultaneousseparation of C2H2, C2H6, and other trace im-purities fromC2H4 with a physisorbent couldenhance the energy efficiency of C2H4 pro-duction but is too challenging for classicalphysisorbents. The fundamental limitation

lies in the respective quadrupolemoments andkinetic diameters of the C2 gases; C2H4 (1.5 ×10−26 esu cm2 and 4.1 Å) lies just between C2H2

(7.2 × 10−26 esu cm2 and 3.3 Å) and C2H6 (0.65 ×10−26 esu cm2 and 4.4 Å), which precludes mostphysisorbents from being highly selective (3).The task is compounded when CO2 (4.3 ×

10−26 esu cm2 and 3.3 Å) is also an impurity ina C2 gasmixture, because a physisorbent wouldthen require strong affinity toward C2H2, C2H6,and CO2 versus C2H4. Metal-organicmaterials,also knownasmetal-organic frameworks (MOFs)or porous coordination polymers, have gainedattention for gas separations because of theirtunability over pore size and pore chemistry(4–9). Several studies have addressed theseparation of C2H2, C2H4, C2H6, and CO2 byphysisorbents (e.g., zeolites, activated car-

bon, porous organic frameworks, and MOFs)(10–17), but selectivity that realizes polymer-grade C2H4 production from a quaternary gasmixture (C2H2-C2H4-C2H6-CO2) is still an im-portant goal. Indeed, even for the ternaryC2H2-C2H4-C2H6 mixture, only a recent re-port by Lu and co-workers found discrimina-tion toward C2H4 over C2H2 and C2H6 in theMOF material TJT-100 (18). The task is fur-ther compounded for wet gas streams becausewater vapor can interfere with physisorbentperformance through co-adsorption or hydro-lytic degradation (19). This would necessitatepretreatment of a gasmixture with a desiccantmaterial.We addressed this separation challenge by

developing synergistic sorbent separation tech-nology (SSST), which uses the favorable sorptionproperties of task-specific ultramicroporousphysisorbents, each with ultrahigh selectiv-ity for one of the impurities, to enable one-step production of C2H4 from C2 gas mixtures(Fig. 1A). Such an approach was used to ad-dress the desulfurization of hydrocarbons,but sulfur impurities with strong polarityare much easier to isolate fromhydrocarbons(20). With respect to C2H2 and C2H6 removalfrom C2H4 streams, TIFSIX-2-Cu-i (TIFSIX =TiF6

2–, 2 = 4,4′-dipyridylacetylene, i = inter-penetrated) offers ultraselective C2H2 capture(21, 22) and, as shown below, Zn-atz-ipa (atz =3-amino-1,2,4-triazolate; ipa = isophthalate)(23), exhibits strong affinity for C2H6 overC2H4 and the other impurities. In principle, acombination of these two physisorbents couldsynergistically capture C2H2 and C2H6 in atandem-packed sorbent bed toproducepolymer-grade (>99.9%) C2H4 via physisorption. Further,

RESEARCH

Chen et al., Science 366, 241–246 (2019) 11 October 2019 1 of 5

1Department of Applied Chemistry, School of Naturaland Applied Sciences, Northwestern PolytechnicalUniversity, Xi’an, Shaanxi 710072, P.R. China. 2BernalInstitute and Department of Chemical Sciences, Universityof Limerick, Limerick V94 T9PX, Republic of Ireland.3Department of Chemistry, University of South Florida,Tampa, FL 33620, USA.*These authors contributed equally to this work.†Corresponding author. Email: ckjiscon@nwpu.edu.cn (K.-J.C.);michael.zaworotko@ul.ie (M.J.Z.) ‡Present address: Departmentof Chemical Engineering and Biotechnology, University ofCambridge, Cambridge CB3 0AS, UK. §Present address:Department of Chemistry, Biochemistry, and Physics, Universityof Tampa, Tampa, FL 33606, USA.

• One-step process

• Ambient temperature and pressure

• Low energy consumed for regeneration

• Three-step process

• Noble metal catalyst

• High temperature and pressure for hydrogenation

• High energy consumed for cryogenic distillation

Present technology

SynergisticSorbentSeparationTechnologyGas

mixturein

Caustic sodasolution

Catalytic hydrogenation Distillationtower

A

B

Sorbent 1 Sorbent 2 Sorbent 3

Impurity 1

Ethane

Impurity 2

Acetylene

Impurity 3

Carbon dioxide

Purifiedgasout

Ethylene

Fig. 1. Synergistic sorbent separation technology (SSST) versus present approaches to purifyC2H4. (A) SSST involves an adsorption bed with three task-specific physisorbents to purify the commodity(red) with specific binding sites for each trace impurity (blue, green, yellow). (B) The present process forproducing polymer grade C2H4 involves three energy-intensive steps.

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the addition of SIFSIX-3-Ni (SIFSIX = SiF62–,

3 = pyrazine), an ultraselective CO2 sorbent(19, 24), to the sorbent bed should enable re-moval of trace levels of CO2 from the corre-sponding four-component gasmixture, therebyoffering a one-step process that offers advan-tages over present approaches (Fig. 1). Theselected physisorbents are stable to humidity,but their sorption performance is reduced inthe presence of water vapor (19, 25).TIFSIX-2-Cu-i and SIFSIX-3-Ni belong to a

family of hybrid ultramicroporousmaterials ofgeneral formulaM′FSIX-L-M (M=divalent tran-sitionmetal center; L = dipyridyl organic linker;M′ = Si, Ti, Ge, Zr, Sn). In this family, squarelattice networks are formed by transitionmetalnodes and bipyridyl-type linkers, which arepillared by inorganic linkers to generate primi-tive cubic topology coordination networkswith tunable pore size and chemistry (21, 24).

TIFSIX-2-Cu-i and SIFSIX-3-Ni have previouslybeen shown to exhibit benchmark perform-ance for trace C2H2 (21) and trace CO2 sorp-tion, respectively (19, 26), but their pore sizeand chemistry renders them ill-suited forC2H6-selective sorption. Indeed, we are unawareof any existing sorbents that are even mildlyselective toward C2H6 over CO2, C2H2, and C2H4

(table S1).The ultramicroporous MOF Zn-atz-ipa was

selected in this context given its excellent waterstability and unusual pore chemistry (23); asdetailed below, this pore chemistry makes itsuitable for the intended purpose. To evaluatethe selected sorbents for C2H4 purification, wefirst determined their pure gas adsorption prop-erties. Each sorbent was synthesized accord-ing to previous reports (19, 22, 23). To verifypurity, we collected powder x-ray diffraction(XRD) patterns and sorption data at cryogenic

temperatures on as-synthesized materialsafter activation (figs. S1 and S2). Single-gasisotherms at 273 and 298 K were collected to1 bar for TIFSIX-2-Cu-i, SIFSIX-3-Ni, and Zn-atz-ipa (figs. S3 to S5). As shown in Fig. 2B, at298 K and 1 bar, TIFSIX-2-Cu-i exhibited lessuptake for C2H6 (2.1 mmol/g) than for C2H4

(2.6 mmol/g), CO2 (4.3 mmol/g), and C2H2

(4.1 mmol/g). C2H2 exhibited the highest up-take from 0 to 0.8 bar for TIFSIX-2-Cu-i. Inthe case of SIFSIX-3-Ni, CO2 exhibited thehighest uptake at 298 K below 0.2 bar (Fig.2C). For Zn-atz-ipa, all four gases showedsimilar uptake (1.8 to 2.0 mmol/g) at 1 barand 298K (Fig. 2A). However, from0 to 0.4 bar,wemeasured higher uptake for C2H6 over CO2,C2H2, and C2H4.To quantify the strength of sorbent-sorbate

interactions, we fit 273 and 298 K sorptiondata by the virial equation (figs. S6 to S11) and

Chen et al., Science 366, 241–246 (2019) 11 October 2019 2 of 5

Fig. 2. Structures of physisorbents used herein and their singlecomponent gas sorption properties. (A to C) Adsorption of CO2 (blacksquares), C2H2 (green stars), C2H4 (red triangles), and C2H6 (blue circles) at298 K for Zn-atz-ipa (A), TIFSIX-2-Cu-i (B), and SIFSIX-3-Ni (C). (D to F)Structures of Zn-atz-ipa (D), TIFSIX-2-Cu-i (E), and SIFSIX-3-Ni (F). (G) TheConnolly surface of Zn-atz-ipa with probe radius of 2.0 Å. (H) Isosteric heat of

CO2 (black), C2H2 (green), C2H4 (red), and C2H6 (blue) in SIFSIX-3-Ni,Zn-atz-ipa, and TIFSIX-2-Cu-i. The “strong binding” threshold of 40 kJ/mol ishighlighted with a dashed line. (I) Selectivity for adsorbates in SIFSIX-3-Ni(CO2 over C2H2/C2H4/C2H6), Zn-atz-ipa (C2H6 over C2H4/C2H2/CO2), andTIFSIX-2-Cu-i (C2H2 over CO2/C2H4/C2H6) at 298 K and 1 bar for 1:1 gasmixtures from ideal adsorbed solution theory.

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calculated the isosteric heat of adsorption (Qst)according to the Clausius-Clapeyron equation.Qst values at low loading of the four gases inTIFSIX-2-Cu-i, SIFSIX-3-Ni, and Zn-atz-ipa arecompared in Fig. 2H. Full Qst curves for thefour gases in the three ultramicroporous sor-bents aregiven in figs. S12 toS14and summarizedin table S2. Each sorbent exhibited strong se-lectivity for one gas over the other three accord-ing to Qst: CO2@SIFSIX-3-Ni (50.9 kJ/mol),C2H6@Zn-atz-ipa (45.8 kJ/mol), and C2H2@TIFSIX-2-Cu-i (46.3 kJ/mol) (Fig. 2H, dashedline). These results indicate that, at least in prin-ciple, CO2, C2H2, and C2H6 in a four-componentgasmixture includingC2H4 should be selectivelycaptured by SIFSIX-3-Ni, TIFSIX-2-Cu-i, andZn-atz-ipa, respectively. The pure gas sorptionperformance of the three selected sorbentsthereforemet the needed criteria for a one-stepSSST process.The gas adsorption selectivity at 298 K and

1 bar was calculated for pairs of adsorbates in1:1 gas mixtures using ideal adsorbed solutiontheory (27, 28). Detailed fitting parameters areprovided in figs. S15 to S20 and tables S3 to S5.As shown in Fig. 2I, TIFSIX-2-Cu-i and SIFSIX-3-Ni exhibited high adsorption selectivity forC2H2 and CO2, respectively, over the other threegases. Indeed, newbenchmark selectivity valueswere found under these or similar conditions(13, 29): C2H2/C2H4 (49) andC2H2/C2H6 (98) in

TIFSIX-2-Cu-i; CO2/C2H4 (103) and CO2/C2H6

(308) in SIFSIX-3-Ni. High selectivity was alsocalculated for CO2/C2H2 (6.1 for C2H2/CO2 byTIFSIX-2-Cu-i, 6.9 for CO2/C2H2 by SIFSIX-3-Ni) (22). Zn-atz-ipa exhibited selective C2H6

adsorption with a selectivity of 1.7 for C2H6/C2H2, 2 for C2H6/C2H4, and 5 for C2H6/CO2.Thus,althoughZn-atz-ipa is a physisorbent, it exhibitedselective adsorptionofC2H6overC2H4,C2H2, andCO2; we consider this result unexpected becauseC2H6 tends to be weakly adsorbed as a conse-quence of its low quadrupole moment.To better understand the interactions of the

four gases with the three sorbents, we con-ducted grand canonical Monte Carlo (GCMC)simulations. Final optimized results for SIFSIX-3-Ni and TIFSIX-2-Cu-i for C2H2 and CO2 wereconsistent with earlier reports (21, 30). Binding-site information for all gases is given in Fig. 3and figs. S21 to S24. In SIFSIX-3-Ni, CO2 bind-ing is driven by interactions with four electro-negative F atoms from four independent SiF6

2–

anions. C2H2 was trapped through multipleC-H···F interactions with H···F distances of3.3 to 4.5 Å between C2H2 and eight SiF6

2–

anions. In contrast, C2H4 and C2H6 exhibitedsimultaneous interactions with two and sixSiF6

2– anions, respectively. Although there arefewer contacts with anions, shorter distancesof 2.51 and 2.62 Å for C2H4 suggest favorableC2H4 binding over C2H6 (2.59 to 2.76 Å).

The overall trend of adsorption energy fromcalculations, CO2 > C2H2 > C2H4 > C2H6, is fullyconsistent with experimental data. In TIFSIX-2-Cu-i, C2H2, C2H4, and C2H6 are localized sothat every molecule could interact with twoTiF6

2– anions through C-H···F interactions.However, C2H2 had shorter contacts (2.46 and2.50 Å) relative to C2H4 (2.45 and 2.52 Å) andC2H6 (2.62 and 2.90 Å). Moreover, the moreacidic C2H2 molecule (pKa = 26, versus C2H4,pKa = 45, and C2H6, pKa = 62) would be ex-pected to form stronger hydrogen bonds. ForTIFSIX-2-Cu-i, CO2 molecules interact withtwo F atoms from one TiF6

2– anion, with shortinteraction distances between the C atom ofCO2 and the F atoms of the TiF6

2– anion (2.65and 3.48 Å). The calculated hierarchy in TIFSIX-2-Cu-i was C2H2 > CO2 > C2H4 > C2H6.In Zn-atz-ipa, all six H atoms of one C2H6

molecule interacted with the pore surface. Thistight-fitting binding site helps to explain thehigh adsorption energy of 42.2 kJ/mol fromGCMC calculations, a value near the experimen-tal value of 45.8 kJ/mol. In contrast, smallermolecules such as C2H4, C2H2, and CO2 onlyinteracted through two or three close con-tacts, and, although amino groups are con-sidered to improve CO2 binding, the aminogroup of the atz ligand was not exposed onthe pore surface. Thus, CO2 binding was weakand the strength of interactions in Zn-atz-ipa

Chen et al., Science 366, 241–246 (2019) 11 October 2019 3 of 5

Fig. 3. Molecular simulation and periodic density functional theory calculations. (A to L) C2H2 [(A), (E), and (I)], C2H4 [(B), (F), and (J)], C2H6 [(C), (G), and(K)], and CO2 [(D), (H), and (L)] binding sites in SIFSIX-3-Ni (top), TIFSIX-2-Cu-i (middle), and Zn-atz-ipa (bottom). Closest contacts between framework atomsand gas molecules are defined by the distance (in angstroms) between the H atom of hydrocarbons and the closest framework atoms. Adsorbed C2 and CO2

molecules are presented in space-filling display mode (C, gray; H, white; O, red; N, blue; F, cyan; Si, yellow; Ni, lavender; Ti, silver; Cu, gold; Zn, dark gray).

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Chen et al., Science 366, 241–246 (2019) 11 October 2019 4 of 5

Fig. 4. Experimental column breakthrough results. (A and B) Experimentalcolumn breakthrough curves for C2H2/C2H4/C2H6 separation (1:1:1 mixture) onTIFSIX-2-Cu-i and Zn-atz-ipa at 298 K and 1 bar. Breakthrough experiments wereconducted in a column (inside diameter, 8 mm) at a flow rate of 2.1 ml/min.(C) Experimental column breakthrough curves for C2H2/C2H4/C2H6 separation(1:1:1 mixture) on a tandem-packed column of TIFSIX-2-Cu-i (~250 mg) andZn-atz-ipa (~600 mg) at 298 K and 1 bar. The x axis is displayed as minutes pergram of TIFSIX-2-Cu-i + Zn-atz-ipa. The orange dashed line highlights the cutofftime for C2H4 with purity >99.9% in this and other plots. (D) Experimental columnbreakthrough curves for C2H2/C2H4/C2H6 separation (1:49.5:49.5 mixture) on a

tandem-packed column of TIFSIX-2-Cu-i (~120 mg) and Zn-atz-ipa (~1200 mg).(E) SSST sorption beds. From left to right: 1:1 to 1:10 TIFSIX-2-Cu-i + Zn-atz-ipa;1:1.25:10 TIFSIX-2-Cu-i + Zn-atz-ipa + SIFSIX-3-Ni; physical mixture of TIFSIX-2-Cu-i + Zn-atz-ipa after breakthrough experiments. (F) Experimental columnbreakthrough curves for CO2/C2H2/C2H4/C2H6 separation (1:1:1:1 mixture) ona tandem-packed column of TIFSIX-2-Cu-i (~120 mg), SIFSIX-3-Ni (~150 mg),and Zn-atz-ipa (~1200 mg) at 298 K and 1 bar (packing order: SIFSIX-3-Ni@Zn-atz-ipa@TIFSIX-2-Cu-i). (G) The effect of packing order of the SSST sorbentson ethylene purity. (H) Temperature-programmed desorption curves recorded onthe column in (F) at 60°C under He flow of 20 cm3/min.

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followed the sequence C2H6 > C2H4 > C2H2 >CO2. (See supplementary materials for moredetails on these simulations.)We conducted dynamic breakthrough ex-

periments at 298Kona custom-built apparatus(fig. S25) using an equimolar three-componentgas mixture of C2H2/C2H4/C2H6 at a total pres-sure of 1 bar. All sorbents were preactivated byheating under high vacuum before preparingthe breakthrough column. We first conductedcontrol experiments using sorbent beds ofTIFSIX-2-Cu-i or Zn-atz-ipa. C2H2 was selec-tively captured, but C2H4 and C2H6 were notseparated by TIFSIX-2-Cu-i (Fig. 4A). For Zn-atz-ipa (Fig. 4B), C2H6was selectively adsorbed for~10min, but C2H2 andC2H4were not separated.However, SSSTwith a two-component (tandem)bed containing TIFSIX-2-Cu-i and Zn-atz-ipacleanly removed C2H2 and C2H6 with C2H4 at>99.9%purity in the effluent stream (Fig. 4C).By increasing the mass ratio of Zn-atz-ipa overTIFSIX-2-Cu-i from 1:1 to 10:1, breakthroughtimes of C2H2 and C2H6 were optimized forthe production of pure C2H4 using SSST (Fig.4E and figs. S26 to S29), which suggests thatthe adsorption capacities of the two adsorbentshad been fully used in the case of the 10/1 ratio.The four-component equimolar mixture

of C2H2/C2H4/C2H6/CO2 was studied usingSIFSIX-3-Ni in a three-component sorbent bed.A ratio of 1:1.25:10 (TIFSIX-2-Cu-i, 120mg; Zn-atz-ipa, 1.2 g; SIFSIX-3-Ni, 150mg)was adoptedon the basis of the single-component sorptiondata. Breakthrough results revealed that CO2,C2H6, and C2H2 were captured (Fig. 4F), pro-ducing polymer-grade C2H4 as effluent (workingcapacity 0.14 mmol/g). The breakthrough se-quence follows the order C2H4/C2H6/CO2/C2H2 at 20.3, 24.6, 24.9, and 28.3 min, respec-tively. Regeneration of the SSST columnunderHe flow (20 ml/min, 1 hour, 60°C) revealed un-changed performance after nine cycles (fig. S30).Tests on the individual sorbents showed facileregenerationwith no capacity loss after 10 cycles(figs. S49 to S51). The low energy footprint of theSSST columns was validated by temperature-programmed desorption experiments (Fig. 4Hand figs. S52B to S59B).In industrial C2 hydrocarbon gas streams,

C2H2 typically makes up only ~1% of the totalflow. To examine the performance of SSSTwith more industrially relevant and chal-lenging gas mixtures, we also tested C2H2/C2H4/C2H6 (1:49.5:49.5) and C2H2/C2H4/C2H6/CO2 (1:33:33:33) gas mixtures. Polymer-gradeC2H4 with working capacities of 0.32 and0.10 mmol/g was harvested from 1:49.5:49.5and 1:33:33:33 gas mixtures, respectively (Fig.4D and fig. S31). The uptake of C2H6 revealed by

its pure gas isotherm with Zn-atz-ipa at 0.495versus 0.33 bar contributed to the higher work-ing capacity of the 1:49.5:49.5 gas mixture.The effect of packing order on SSST per-

formance was assessed with six parallel SSSTcolumns and breakthrough experiments witha 1:1:1:1 gas mixture at 298 K and 1 bar. Theresults (table S6) revealed the importanceof packing order (Fig. 4G and figs. S55A toS59A). SIFSIX-3-Ni@Zn-atz-ipa@TIFSIX-2-Cu-i afforded the highest working capacity(0.14 mmol/g), whereas two other combina-tions, both with Zn-atz-ipa as the final sorbent(SIFSIX-3-Ni@TIFSIX-2-Cu-i@Zn-atz-ipa andTIFSIX-2-Cu-i@SIFSIX-3-Ni@Zn-atz-ipa), failed(Fig. 4H). The effects of different selectivityvalues, kinetics, and co-adsorption (22) werelikely the cause of this observation. Particle sizeand amount of sorbent had little effect, withsmaller particle size and larger sample amountsresulting in slightly improved C2H4 purification(figs. S33 to S47). A columnwith looser packing,however, offered much-reduced performance(fig. S48). The use of a physical mixture alsofailed. When we used 120 mg of TIFSIX-2-Cu-iand 1200mg of Zn-atz-ipa on an equimolar gasmixture of C2H2/C2H4/C2H6, C2H2 was not effec-tively removed before C2H4 breakthrough (fig.S32). Further, C2H6 concentration was not re-duced to the required specification of <0.1%.We were able to take advantage of the var-

iations in pore geometry and pore chemistryof three ultramicroporous sorbents to addressone-step C2H4 purification using SSST. Thechoice of task-specific ultraselective sorbentsin tandem-packed sorbent beds of the typeused here is unlikely to be limited to the threesorbents or target gas we investigated. Sor-bents with higher selectivity, higher uptakecapacity, or both could likely be substitutedto optimize overall performance. The strongperformance of SSST with respect to the puri-fication of C2 gas mixtures and the availabilityof an ever-increasing number of ultraselectivephysisorbents suggests that the scope of SSSTis likely to be broad enough to address the highenergy footprint of other industrial commod-ity purifications.

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(2015).

ACKNOWLEDGMENTS

We thank J.-W. Cao and S. Sanda for synthesis of some samplesand particle size analysis, respectively; T. Curtin (UL) for use of herdynamic breakthrough equipment; and the Analytical and TestingCenter of Northwestern Polytechnical University for access to thePXRD testing facility. Funding: Supported by Science FoundationIreland awards 13/RP/B2549 and 16/IA/4624 (M.J.Z.); NationalNatural Science Foundation of China grant 21805227 andFundamental Research Funds for the Central Universities grant3102017jc01001 (K.-J.C.); NSF grant DMR-1607989, includingsupport from the Major Research Instrumentation Program (awardCHE-1531590) (T.P., K.A.F., and B.S.); and ACS PetroleumResearch Fund grant 56673-ND6 (B.S.). Computational resourceswere made available by XSEDE grant TG-DMR090028 and byResearch Computing at the University of South Florida. Authorcontributions: M.J.Z. and K.-J.C. designed the experiments.K.-J.C., D.G.M., J.K., T.P., B.S., and M.J.Z. co-wrote the paper.K.-J.C. and A.K. synthesized compounds. K.-J.C. performed thegas adsorption experiments and data analysis. D.G.M. andS.M. conducted dynamic breakthrough experiments. S.M.conducted sorption cycling and temperature programmeddesorption experiments. T.P., K.A.F., and B.S. conducted molecularsimulation. experiments. All authors discussed the results andcommented on the manuscript. Competing interests: K.-J.C.,D.G.M., S.M., A.K., and M.J.Z. are inventors on patent applicationEP19197407.0 submitted by University of Limerick that coversthe use of ultramicroporous sorbents for one-step purification ofgas mixtures. Data and materials availability: All data areavailable in the manuscript and supplementary materials.

SUPPLEMENTARY MATERIALS

science.sciencemag.org/content/366/6462/241/suppl/DC1Materials and MethodsFigs. S1 to S59Tables S1 to S6References (31–44)

30 April 2019; resubmitted 4 August 2019Accepted 19 September 201910.1126/science.aax8666

Chen et al., Science 366, 241–246 (2019) 11 October 2019 5 of 5

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mixtureSynergistic sorbent separation for one-step ethylene purification from a four-component

Qiu-Yu Zhang and Michael J. ZaworotkoKai-Jie Chen, David G. Madden, Soumya Mukherjee, Tony Pham, Katherine A. Forrest, Amrit Kumar, Brian Space, Jie Kong,

DOI: 10.1126/science.aax8666 (6462), 241-246.366Science 

, this issue p. 241Scienceethylene pure enough for making polymers.physisorbents that are selective for one of these four gases. A series of sorbents in a packed-bed geometry produced

use a mixture of microporous metal-organic frameworket al.dioxide, is an energy-intensive process. Chen Purification of ethylene from other gases produced during its synthesis, such as acetylene, ethane, and carbon

Selecting for ethylene

ARTICLE TOOLS http://science.sciencemag.org/content/366/6462/241

MATERIALSSUPPLEMENTARY http://science.sciencemag.org/content/suppl/2019/10/09/366.6462.241.DC1

REFERENCES

http://science.sciencemag.org/content/366/6462/241#BIBLThis article cites 40 articles, 4 of which you can access for free

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