Thermodynamically Controlled Linker Installation in FlexibleZirconium Metal−Organic FrameworksPublished as part of a Crystal Growth and Design virtual special issue on Crystalline Functional Materials inHonor of Professor Xin-Tao Wu

Christina T. Lollar, Jiandong Pang,* Jun-sheng Qin, Shuai Yuan, Joshua A. Powell,and Hong-Cai Zhou*

Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States

*S Supporting Information

ABSTRACT: A series of metal−organic frameworks (MOFs) (PCN-606-OH-TPDC, PCN-606-OMe-TPDC, PCN-606-OH-EDDB, andPCN-606-OMe-EDDB) are synthesized through linker installationonto open sites of 8-connected Zr6 clusters in PCN-606-R (where R= −OH or −OMe) parent frameworks of differing flexibilities. The twopostsynthetically installed linear linkers possess slight differences inlength and bulk, which result in a noticeable difference in the installationtemperatures, reflective of a different thermodynamic barrier toincorporation into PCN-606-R. The X-ray crystallographic data as wellas the N2 adsorption properties of these four newly produced MOFs areexplored and compared to gain a more comprehensive understanding ofthe implications that this difference in linker size and bulk have duringinsertion into flexible MOFs.

■ INTRODUCTION

The ability to synthesize metal−organic frameworks (MOFs)with desired variations in chemical and thermal stability,porosity, and pore shape has enabled their application indisciplines spanning gas storage,1−5 separations,1,4−10 catal-ysis,5,10−16 and sensing.5,10,17−22 Through judicious tuning oftheir metal cluster and organic linker components, MOFs, alsoknown as porous coordination networks (PCNs), may beproduced with diverse physical and chemical properties.23−27

This diversity of composition through multiple structuralvariables is what has given the MOF research field theunremitting vigor it boasts today. For example, flexibility maybe introduced into a framework through the adoption oforganic linkers with conformational flexibility, metal clusterscapable of deformations, or through cooperative effects.23−27

These resulting flexible MOFs are often capable of maintainingporosity and crystallinity upon guest molecule evacuation,transforming between different states of porosity: open pore,narrow pore, large pore, or closed pore. These functionalmaterials therefore possess particular advantages over rigidMOFs. These may be noticeable in applications that benefitfrom framework pore size variations such as sensing, if achange in pore state is accompanied by a detectable radiativeexpression, selective separations, particularly when one porestate can preferentially accept a particular guest molecule overa competing guest molecule, and controlled drug release inbiological systems.

Regrettably, exerting deliberate control over MOF structurescan sometimes pose a significant challenge because manyMOFs are synthesized through one-pot solvothermal methods.These methods are often considered black box-like, wherebythe exact mechanisms of formation still require furtherinvestigation.25,26,28 In addition, a number of complicationsmay arise with solvothermal synthesis: separate domains mayform when a homogeneous structure is desired, one phase maydominate when another is expected, or a crystalline powdermay form when a single crystal is necessary for more facilecharacterization. The creation of extremely stable and highlycrystalline frameworks is hindered by the lack of bondreversibility in stable metal−ligand bonds, while the creationof less stable structures is energetically disfavored, and so othermeans are necessary to arrive at these materials. Postsyntheticmodification (PSM) methods, including metal metathesis,linker exchange, cluster metalation, linker installation, andlinker labilization, may be employed to exert control overMOF structures while avoiding these obstacles.23,27,29−35

Although defects may be inherent in some MOFs, defectengineering to produce additional defects may also be used toadd an extra dimension of structural modification.24,27,33,36−38

This is especially important because defects are a prerequisitefor postsynthetic linker installation onto metal clusters. Linker

Received: October 31, 2018Revised: March 3, 2019Published: March 14, 2019

Article

pubs.acs.org/crystalCite This: Cryst. Growth Des. 2019, 19, 2069−2073

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installation is a mild, kinetically driven PSM method thatreplaces aqua/hydroxo pairs on the “open sites” of a metalcluster node (defect site) with organic ligands featuring charge-compensating groups. In this way, linkers of appropriate sizeand topicity may be precisely placed within a preexisting MOF.However, the size that qualifies as appropriate may bemalleable in the case of flexible MOFs and dependent on thetemperature of installation employed.

■ RESULTS AND DISCUSSIONPCN-606 is a stable MOF that crystallizes in the orthorhombicCmmm space group producing a 4,8-c scu-net topology with atopological point symbol of {416.612}{44.62}2 (Figure 1c).

PCN-606 was selected as a platform for linker insertion for twokey reasons. First, PCN-606 possesses tetratopic linkers and 8-connected Zr6 clusters (Figure 1a,b) with exceptional stability,variable connectivity, and open metal sites for postsyntheticlinker installation (Figure 1a−c). Second, the flexibility ofPCN-606 has already been established experimentally by ourgroup through measurement along the channel pores beforeand after partial desolvation (Figure 1d,e, and Table S4.1) andby subsequent use as a bromine nanocontainer for room-temperature brominations, whereby MOFs with moreaccommodating, flexible pores showed higher bromineuptake.39 In particular, PCN-606-OH and PCN-606-OMewere selected, whose Zr6(μ3-O)4(μ3-OH)4(H2O)4(OH)4nodes are connected by 4,4′OH-H4TPCB (4,4′-dihydroxybi-phenyl-3,3′,5,5′-tetra(phenyl-4-carboxylic acid)) or 4,4′-OMe-H4TPCB (4,4′-dimethoxybiphenyl-3,3′,5,5′-tetra(phenyl-4-carboxylic acid)), respectively. The functional groups in the4- and 4′-positions of these ligands should encourage theadoption of the scu topology by maintaining the coplanarity ofthe inner biphenyl rings in a D2h symmetry. These MOFscontain large one-dimensional pore channels, a high degree offlexibility, and 8-connected metal nodes with inherent defectsprime for the postsynthetic installation of additional linkers.Two ligands, H2EDDB (4,4′-(ethyne-1,2-diyl)dibenzoic

acid) and Me2TPDC (2′,5′-dimethylterphenyl-4,4″-dicarbox-ylate) whose structures are shown in Figure 2a, were selectedfor insertion into PCN-606-OH and PCN-606-OMe (a generalstructure of PCN-606-R with crystallographic axes labeled canbe found in Figure 2b). The OH−/H2O ligands on the metalclusters of these MOFs may be removed relatively easily toallow for postsynthetic integration of the linear dicarboxylateligands since ditopic ligands are more easily held in aframework than monotopic solvent “ligands”. We have recentlyreported on PCN-606-OH with postsynthetically installedTPDC linkers (PCN-606-OH-TPDC) in a separate pursuit ofdeveloping more complex, multicomponent MOFs.40

Me2TPDC is longer and bulkier than H2EDDB, and soinsertion of this ligand into a less flexible framework seemedless promising.It was found that H2EDDB can be successfully incorporated

into PCN-606-OH and PCN-606-OMe by soaking the PCN-

Figure 1. Structure and topology of (a) the tetratopic carboxylatestructural ligand and (b) the 8-connected Zr6 cluster that form theparent MOF, PCN-606-R. (c) The structure and topologicalreduction of PCN-606-R. The structures of PCN-606-R with thedifferences in height along the pore in question highlighted (d) beforeand (e) after partial desolvation. A more detailed summation of the X-ray diffraction data may be found in Table S4.1.

Figure 2. (a) Chemical structures and approximate lengths of postsynthetically installed linkers, EDDB and TPDC, with the “a” directioncorresponding to the a-axis once inserted into PCN-606-R, (b) PCN-606-R with axes labeled, and (c) stacked column chart comparing the percentchange in the a (green), b (blue), and c (tan) axes lengths after ligand installation into the parent framework.

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606-R derivatives in a solution of excess ligand in DMF at 80°C to form new MOFs which were termed PCN-606-OH-EDDB and PCN-606-OMe-EDDB. However, when the sameprocedural variables were applied with the Me2TPDC ligand,linker insertion proved unsuccessful. This was attributed to theaforementioned difference in length and bulkiness. Interest-ingly, raising the temperature of linker insertion pushes theflexibility boundaries of the framework. Indeed, it was foundthat when the parent MOF was soaked in a solution of excessMe2TPDC ligand in DMF at 120 °C, the PCN-606-OH-TPDC and PCN-606-OMe-TPDC structures successfullyformed. It is worthwhile to note that we were also able toobtain PCN-606-R-TPDC through a one-pot synthesiscontaining both TPCB and TPDC with ligand insertion ratioscomparable to post synthetic insertion (Table S6.1); however,we were unable to acquire PCN-606-R-EDDB in this manner.Successful installation of the linear linkers was confirmed

with 1H NMR analysis of the decomposed MOF samples.Single-crystal X-ray diffraction (SCXRD) studies revealed thatthe newly formed MOFs were all 4,10-c nets with newtopologies and a point symbol of {416.512.616.7}{44.52}2.Although 1H NMR and SCXRD confirmed the successfulpostsynthetic incorporation of the linear linkers, it could beargued that the increase in temperature produced enhancedflexibility within the linker as it inserts into the MOF. For thisreason, it was important to verify a change in the frameworkitself by observing the change in length of the axis ofinstallation (the a-axis) before and after insertion. Uponincorporation of the slightly less obtrusive H2EDDB ligandinto PCN-606-OH and PCN-606-OMe, the a-axis expandedfrom an initial 18.8 and 19.8 Å to 21.5 Å (14.4% expansion)and 21.6 Å (9.1% expansion) to form PCN-606-OH-EDDBand PCN-606-OMe-EDDB, respectively. The resulting a-axislengths for the −OH and −OMe MOFs are nearly identicalsince the inserted linker is the same. This may suggest thatdistortion in the linker is minimal in comparison to thechanges that occur in the parent MOF. The integration of thelarger Me2TPDC ligand in PCN-606-OH and PCN-606-OMeto form PCN-606-OH-TPDC and PCN-606-OMe-TPDCresults in final a-axis lengths of 23.1 Å (22.9% expansion)and 23.3 Å (17.7% expansion), respectively. Once again, theresulting a-axis lengths of PCN-606-OH-TPDC and PCN-606-OMe-TPDC naturally are very close. The greater a-axisexpansion for the incorporation of the more demandingTPDC linker likely requires a higher energy input in the formof an elevated installation temperature (120 °C as opposed to

80 °C) to help overcome a thermodynamic barrier toformation. As the a-axis expands, the b-axis and c-axis caninterestingly be seen slightly shrinking to compensate.Explicitly, when Me2TPDC extends the a-axis of PCN-606-OH by 4.3 Å (22.9%), the b-axis reduces by 1.3 Å (3.6%) andthe c-axis reduces by 1.0 Å (6.2%). When the same ligand isinserted into PCN-606-OMe with an a-axis extension of 3.5 Å(17.7%), the b-axis shrinks by 1.1 Å (3.1%) and the c-axisshrinks by 0.9 Å (5.4%). The addition of the smaller ligand,H2EDDB, into PCN-606-OH produces a growth in the a-axisby 2.7 Å (14.4%) accompanied by b-axis and c-axis reductionsby 0.7 Å (2.0%) and 0.6 Å (3.7%), respectively. Lastly,insertion of H2EDDB into PCN-606-OMe increases the a-axisby 1.8 Å (9.1%) while concurrently decreasing the b-axis and c-axis by 0.4 Å (1.2%) and 0.5 Å (3.2%), respectively. In allcases, the a-axes shows a larger percentage increase than thesum of the b- and c-axes decrease suggesting an overall increasein size, which will be mentioned later in terms of volume(these percent changes are displayed together for comparisonin Figure 2c). Additionally, the changes in axes lengths aremore dramatic in the case of PCN-606-OH-R′ than for PCN-606-OMe-R’ (where R′ = EDDB or TPDC). It is probable thatthe steric effects in the methoxy- derivative somewhat impedestructural ligand distortion in the framework, leading to smallerchanges in axis lengths. For comparison, it was previouslyreported that the a-axis of PCN-606-OH would shrink byabout 22.3% and the a-axis of PCN-606-OMe would shrink byabout 14.0% upon desolvation. Admittedly, the smallermagnitude of axial changes is also certainly aided by the factthat PCN-606-OMe’s axes lengths were already closer to thoseof the linker-inserted PCN-606-OMe-R’.Although the linkers are installed along the a-axis, it is also

helpful to consider changes in volume in order to understandMOF flexibility. As may be predicted, PCN-606-OH and-OMe have the smallest volumes of about 10 600 Å3 and11 000 Å3. Upon insertion of the smaller EDDB ligand, thisvolume expands by 7.97% and 4.14%, respectively. With theaddition of the bulkier TPDC ligand, volumes expanded by11.4% and 7.68%, respectively. These values are reasonableconsidering the larger size of TPDC as well as the lowerflexibility of PCN-606-OMe compared with PCN-606-OH.More specific crystal data may be found in Table S.4.1.The internal spaces of these MOFs were probed before and

after each ligand installation. Nitrogen sorption isothermsshown in Figure 4 were collected at 77 K (1 atm) andcompared. In the case of both the −OH and −OMe

Figure 3. Schematic representation of the difference in installation temperature required for the successful incorporation of EDDB and TPDC.

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derivatives, N2 uptake follows the same trend as a-axis length,increasing in the order of PCN-606-R < PCN-606-R-EDDB <PCN-606-R-TPDC (where R = −OH or −OMe.) Specifically,PCN-606-OMe shows the lowest uptake at about 280 cm3 g−1,followed by PCN-606-OH at about 498 cm3 g−1, PCN-606-OMe-EDDB at 515 cm3 g−1, PCN-606-OH-EDDB at 558 cm3

g−1, PCN-606-OH-TPDC at 592 cm3 g−1, and PCN-606-OMe-TPDC at 618 cm3 g−1. These translate into BET surfaceareas of 2003 ± 10 m2 g−1 for PCN-606-OMe-TPDC, 2164 ±10 m2 g−1 for PCN-606-OH-TPDC, 2514 ± 10 m2 g−1 forPCN-606-OH-EDDB, and 2388 ± 17 m2 g−1 for PCN-606-OMe-EDDB. It may seem intuitive that adding linkers into aMOF’s pores can increase the available surface area; however, amarked disparity is observed in the amount by which PCN-606-OMe increases in surface area upon linker insertioncompared to PCN-606-OH. This difference is created due tothe abnormally low nitrogen uptake of unmodified PCN-606-OMe. This is likely a consequence of MOF flexibility. If PCN-606-OMe adopts a closed pore state when unmodified andsolvent is evacuated, some surfaces will be inaccessible,resulting in a decreased surface area as measured by nitrogenadsorption. Linker insertion into PCN-606-OMe forces theMOF into an open pore conformation, explaining the moredramatic increase in nitrogen uptake.With the data seeming to point to a difference in

thermodynamic barriers to installation for these two ligands,the thermal stability of the resulting MOFs and their parentswas called into question. Thermogravimetric analysis indicatedthe increased stability of the MOFs after linker insertion, with amore prominent increase in thermal stability in the case ofPCN-606-OMe and derivatives as compared to the lessconspicuous increase in thermal stability for PCN-606-OHMOFs. The data are contained in Figures S8.1 and S8.2.In summary, linker installation into PCN-606-R parent

frameworks has yielded a collection of four MOFs, PCN-606-OH-EDDB, PCN-606-OMe-EDDB, PCN-606-OH-TPDC,and PCN-606-OMe-TPDC. The TPDC linker is bulkier andslightly longer than the EDDB linker, and so a highertemperature was necessary for successful installation. X-raycrystallography provided information on the changes in axislengths and volume upon linker installation, providing generalinsight into the flexibility of the two PCN-606-R derivatives.The reported results highlight two related points, (1) thatsmall differences in linker size may result in significant

discrepancies in thermodynamic barriers to formation and(2) that the size of the linkers a flexible MOF is capable ofaccepting may be adjusted by additional energy input in theform of heat. As of late, the number of interesting studies onpathways and conditions for MOF flexibility have beenincreasing.41,42 Enhancing our understanding of how tomanipulate, explain, and predict flexible MOF behavior willdoubtlessly enable greater control over future functional MOFstructures and behaviors.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acs.cgd.8b01637.

S1. Materials and instrumentation. S2. Ligand synthesis.S3. MOF synthesis. S4. Single crystal X-ray diffraction.S5. Powder X-ray diffraction. S6. 1H NMR spectroscopy.S7. N2 Sorption isotherms. S8. Thermogravimetricanalysis (PDF)

Accession CodesCCDC 1854071 and 1875211−1875213 contain the supple-mentary crystallographic data for this paper. These data can beobtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or bycontacting The Cambridge Crystallographic Data Centre, 12Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■ AUTHOR INFORMATIONCorresponding Authors*(H.C.Z.) E-mail: Zhou@chem.tamu.edu.*(J.P.) E-mail: jdpang@tamu.edu.ORCIDJun-sheng Qin: 0000-0003-2531-552XHong-Cai Zhou: 0000-0002-9029-3788NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis material is based upon work supported by the NationalScience Foundation Graduate Research Fellowship underGrant No. DGE: 1252521 and the Welch Foundation (A-0030). Additionally, this work was supported as part of theCenter for Gas Separations, an Energy Frontier ResearchCenter funded by the U.S. Department of Energy, Office ofScience, Basic Energy Sciences under Award # DE-SC0001015.

■ REFERENCES(1) Li, B.; Wen, H.-M.; Zhou, W.; Chen, B. Porous Metal − OrganicFrameworks for Gas Storage and Separation: What, How, and Why? J.Phys. Chem. Lett. 2014, 5, 3468−3479.(2) Tranchemontagne, D. J.; Park, K. S.; Furukawa, H.; Eckert, J.;Knobler, C. B.; Yaghi, O. M. Hydrogen Storage in New Metal −Organic Frameworks. J. Phys. Chem. C 2012, 116, 13143−13151.(3) An, J.; Rosi, N. Tuning MOF CO2 Adsorption Properties viaCation Exchange. J. Am. Chem. Soc. 2010, 132 (16), 5578−5579.(4) Li, J.-R.; Kuppler, R. J.; Zhou, H. C. Selective Gas Adsorptionand Separation in Metal-Organic Frameworks. Chem. Soc. Rev. 2009,38 (5), 1477−1504.(5) Jiao, L.; Wang, Y.; Jiang, H. L.; Xu, Q. Metal−OrganicFrameworks as Platforms for Catalytic Applications. Adv. Mater. 2018,30 (37), 1703663.

Figure 4. N2 adsorption isotherms for PCN-606-R, PCN-606-R-EDDB, and PCN-606-R-EDDB where R is −OH or −OMe.

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(6) Li, J.; Sculley, J.; Zhou, H. Metal−Organic Frameworks forSeparations. Chem. Rev. 2012, 112, 869−932.(7) Herm, Z. R.; Bloch, E. D.; Long, R. Hydrocarbon Separations inMetal − Organic Frameworks. Chem. Mater. 2014, 26, 323−338.(8) Lin, R. B.; Xiang, S.; Xing, H.; Zhou, W.; Chen, B. Exploration ofPorous Metal-Organic Frameworks for Gas Separation andPurification. Coord. Chem. Rev. 2019, 378, 87−103.(9) Li, X.; Liu, Y.; Wang, J.; Gascon, J.; Li, J.; Van Der Bruggen, B.Metal-Organic Frameworks Based Membranes for Liquid Separation.Chem. Soc. Rev. 2017, 46 (23), 7124−7144.(10) Liu, X.; Lin, H.; Xiao, Z.; Fan, W.; Huang, A.; Wang, R.; Zhang,L.; Sun, D. Multifunctional Lanthanide-Organic Frameworks forFluorescent Sensing, Gas Separation and Catalysis. Dalt. Trans. 2016,45 (9), 3743−3749.(11) Xiong, L.; Zhang, H.; He, Z.; Wang, T.; Xu, Y.; Zhou, M.;Huang, K. Acid-Base Bifunctional Amphiphilic Organic Nanotubes asa Catalyst for One-Pot Cascade Reactions in Water. New J. Chem.2018, 42 (2), 1368−1372.(12) Liu, H.; Xi, F. G.; Sun, W.; Yang, N. N.; Gao, E. Q. Amino- andSulfo-Bifunctionalized Metal-Organic Frameworks: One-Pot TandemCatalysis and the Catalytic Sites. Inorg. Chem. 2016, 55 (12), 5753−5755.(13) Climent, M. J.; Corma, A.; Iborra, S.; Sabater, M. J.Heterogeneous Catalysis for Tandem Reactions. ACS Catal. 2014, 4(3), 870−891.(14) Comito, R. J.; Fritzsching, K. J.; Sundell, B. J.; Schmidt-Rohr,K.; Dinca , M. Single-Site Heterogeneous Catalysts for OlefinPolymerization Enabled by Cation Exchange in a Metal-OrganicFramework. J. Am. Chem. Soc. 2016, 138 (32), 10232−10237.(15) Zhang, Y.; Yang, X.; Zhou, H. C. Synthesis of MOFs forHeterogeneous Catalysis via Linker Design. Polyhedron 2018, 154,189−201.(16) Johnson, B. A.; Bhunia, A.; Fei, H.; Cohen, S. M.; Ott, S.Development of a UiO-Type Thin Film Electrocatalysis Platform withRedox-Active Linkers. J. Am. Chem. Soc. 2018, 140 (8), 2985−2994.(17) Kumar, P.; Deep, A.; Kim, K. H. Metal Organic Frameworks forSensing Applications. TrAC, Trends Anal. Chem. 2015, 73, 39−53.(18) Kreno, L. E.; Leong, K.; Farha, O. K.; Allendorf, M.; VanDuyne, R. P. V.; Hupp, J. T. Metal−Organic Framework Materials asChemical Sensors. Chem. Rev. 2012, 112, 1105−1125.(19) Campbell, M. G.; Sheberla, D.; Liu, S. F.; Swager, T. M.; Dinca,M. Cu3(Hexaiminotriphenylene)2: An Electrically Conductive 2DMetal-Organic Framework for Chemiresistive Sensing. Angew. Chem.,Int. Ed. 2015, 54 (14), 4349−4352.(20) Lustig, W. P.; Mukherjee, S.; Rudd, N. D.; Desai, A. V.; Li, J.;Ghosh, S. K. Metal-Organic Frameworks: Functional Luminescentand Photonic Materials for Sensing Applications. Chem. Soc. Rev.2017, 46 (11), 3242−3285.(21) Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T.Luminescent Metal-Organic Frameworks. Chem. Soc. Rev. 2009, 38(5), 1330−1352.(22) Wang, R.; Liu, X.; Huang, A.; Wang, W.; Xiao, Z.; Zhang, L.;Dai, F.; Sun, D. Unprecedented Solvent-Dependent Sensitivities inHighly Efficient Detection of Metal Ions and NitroaromaticCompounds by a Fluorescent Barium Metal-Organic Framework.Inorg. Chem. 2016, 55 (4), 1782−1787.(23) Sun, Y.; Zhou, H. C. Recent Progress in the Synthesis of Metal-Organic Frameworks. Sci. Technol. Adv. Mater. 2015, 16 (5), 054202.(24) Dissegna, S.; Epp, K.; Heinz, W. R.; Kieslich, G.; Fischer, R. A.Defective Metal-Organic Frameworks. Adv. Mater. 2018, 30 (37),1870280.(25) Stock, N.; Biswas, S. Synthesis of Metal-Organic Frameworks(MOFs): Routes to Various MOF Topologies, Morphologies, andComposites. Chem. Rev. 2012, 112, 933−969.(26) Yuan, S.; Qin, J. S.; Li, J.; Huang, L.; Feng, L.; Fang, Y.; Lollar,C.; Pang, J.; Zhang, L.; Sun, D. Retrosynthesis of Multi-ComponentMetal-Organic Frameworks. Nat. Commun. 2018, 9 (1), No. 808,DOI: 10.1038/s41467-018-03102-5.

(27) Lollar, C. T.; Qin, J. S.; Pang, J.; Yuan, S.; Becker, B.; Zhou, H.C. Interior Decoration of Stable Metal-Organic Frameworks.Langmuir 2018, 34 (46), 13795−13807.(28) Ma, S.; Parman, J. A. Elaboration and Applications of Metal-Organic Frameworks; World Scientific Publishing Co. Pte. Ltd., 2018.(29) Tanabe, K. K.; Cohen, S. M. Postsynthetic Modification ofMetal-Organic Frameworks - A Progress Report. Chem. Soc. Rev.2011, 40 (2), 498−519.(30) Verde-Sesto, E.; Merino, E.; Rangel-Rangel, E.; Corma, A.;Iglesias, M.; Sanchez, F. Postfunctionalized Porous PolymericAromatic Frameworks with an Organocatalyst and a TransitionMetal Catalyst for Tandem Condensation-Hydrogenation Reactions.ACS Sustainable Chem. Eng. 2016, 4 (3), 1078−1084.(31) Marshall, R. J.; Forgan, R. S. Postsynthetic Modification ofZirconium Metal-Organic Frameworks. Eur. J. Inorg. Chem. 2016,2016, 4310−4331.(32) Jambovane, S. R.; Nune, S. K.; Kelly, R. T.; McGrail, B. P.;Wang, Z.; Nandasiri, M. I.; Katipamula, S.; Trader, C.; Schaef, H. T.Continuous, One-Pot Synthesis and Post-Synthetic Modification ofNanoMOFs Using Droplet Nanoreactors. Sci. Rep. 2016, 6, 36657.(33) Kirchon, A.; Feng, L.; Drake, H. F.; Joseph, E. A.; Zhou, H.-C.From Fundamentals to Applications: A Toolbox for Robust andMultifunctional MOF Materials. Chem. Soc. Rev. 2018, 47, 8611−8638.(34) Liu, C.; Zeng, C.; Luo, T. Y.; Merg, A. D.; Jin, R.; Rosi, N. L.Establishing Porosity Gradients within Metal-Organic FrameworksUsing Partial Postsynthetic Ligand Exchange. J. Am. Chem. Soc. 2016,138 (37), 12045−12048.(35) Guillerm, V.; Xu, H.; Albalad, J.; Imaz, I.; Maspoch, D.Postsynthetic Selective Ligand Cleavage by Solid−Gas PhaseOzonolysis Fuses Micropores into Mesopores in Metal−OrganicFrameworks. J. Am. Chem. Soc. 2018, 140 (44), 15022−15030.(36) Yuan, L.; Tian, M.; Lan, J.; Cao, X.; Wang, X.; Chai, Z.; Gibson,J. K.; Shi, W. Defect Engineering in Metal-Organic Frameworks: ANew Strategy to Develop Applicable Actinide Sorbents. Chem.Commun. 2018, 54 (4), 370−373.(37) Park, H.; Kim, S.; Jung, B.; Park, M. H.; Kim, Y.; Kim, M.Defect Engineering into Metal-Organic Frameworks for the Rapid andSequential Installation of Functionalities. Inorg. Chem. 2018, 57 (3),1040−1047.(38) Fang, Z.; Bueken, B.; De Vos, D. E.; Fischer, R. A. Defect-Engineered Metal-Organic Frameworks. Angew. Chem., Int. Ed. 2015,54 (25), 7234−7254.(39) Pang, J.; Yuan, S.; Du, D.; Lollar, C.; Zhang, L.; Wu, M.; Yuan,D.; Zhou, H. C.; Hong, M. Flexible Zirconium MOFs as Bromine-Nanocontainers for Bromination Reactions under Ambient Con-ditions. Angew. Chem., Int. Ed. 2017, 56, 14622−14626.(40) Pang, J.; Yuan, S.; Qin, J.; Wu, M.; Lollar, C. T.; Li, J.; Huang,N.; Li, B.; Zhang, P.; Zhou, H.-C. Enhancing Pore-EnvironmentComplexity Using a Trapezoidal Linker: Toward Stepwise Assemblyof Multivariate Quinary Metal− Organic Frameworks. J. Am. Chem.Soc. 2018, 140, 12328−12332.(41) Parent, L. R.; Pham, C. H.; Patterson, J. P.; Denny, M. S.;Cohen, S. M.; Gianneschi, N. C.; Paesani, F. Pore Breathing of Metal-Organic Frameworks by Environmental Transmission ElectronMicroscopy. J. Am. Chem. Soc. 2017, 139 (40), 13973−13976.(42) Schneemann, A.; Vervoorts, P.; Hante, I.; Tu, M.;Wannapaiboon, S.; Sternemann, C.; Paulus, M.; Wieland, D. C. F.;Henke, S.; Fischer, R. A. Different Breathing Mechanisms in FlexiblePillared-Layered Metal-Organic Frameworks: Impact of the MetalCenter. Chem. Mater. 2018, 30 (5), 1667−1676.

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