Stabilizing the Extrinsic Porosity in Metal–Organic Cages-Based Supramolecular Framework by In Situ Catalytic Polymerization

Open AccessCCS ChemistryRESEARCH ARTICLE1 May 2021Stabilizing the Extrinsic Porosity in Metal–Organic Cages-Based Supramolecular Framework by In Situ Catalytic Polymerization Guoliang Liu†, Mi Zhou†, Kongzhao Su, Ravichandar Babarao, Daqiang Yuan and Maochun Hong Liu† State Key Laboratory of Structural Chemistry, Fujian Institute Research on Structure Matter, Chinese Academy Sciences, Fuzhou 350002 †G. Liu M. Zhou contributed equally to this work.Google Scholar More articles author , Zhou† Su Google Babarao Commonwealth Scientific Industrial Organization (CSIRO) Manufacturing, Melbourne, VIC 3169 School Science, RMIT University, 3001. *Corresponding author: E-mail Address: [email protected] University Beijing 100049 https://doi.org/10.31635/ccschem.020.202000263 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd favoritesTrack Citations ShareFacebookTwitterLinked InEmail Porous supramolecular frameworks based metal–organic cages (MOCs) usually have poor structural stability after activation. This issue narrows scope their potential applications, particularly for inclusion guest molecules that demand high porosity. Herein, authors reported stabilization a mesoporous zirconium MOC-based framework with an situ catalytic polymerization strategy. Due passivation effect imparted strategy, introduced polymer is primarily distributed surface crystals, which results hybrid material retaining its crystallinity permanent A preliminary application type stabilized shows among frameworks, it has highest high-pressure methane uptake. Such facile strategy may provide general way stabilize fragile porous materials facilitate exploration applications. Download figure PowerPoint Introduction Metal-organic attracted increasing attention1 numerous such as substrates hierarchical structures,2,3 cavity-induced catalysis,4–9 sensitive species,10 gas adsorption.11 To extend homogeneous solution behavior heterogeneous solid state, several studies focused assembling MOCs into through relatively weak interactions been reported.12–18 both intrinsic porosity ( Pore A), emerging from shape-persistent voids MOCs, extrinsic B), depends MOC packing style experiencing Supporting Information Figure S3). B can be rationally designed region expanding size A. The resultant are desirable applications systematically demonstrated other materials,19–21 (MOFs). However, due intermolecular between resulting prone collapse upon activation,22 leading pore blockage limitations applicability areas requiring solid-state Cross-linking active sites embedded shown effectively maintain activation.23 limited accessible sites. As result, generally applicable methods efficiently increase demand. cavities MOFs powerful fabricate composite materials. By taking advantage regulated nanochannels MOFs, unique assemblies implemented, polymeric particles shape replication were realized MOF template degradation.24–26 induced polymers also exert influence synergistically develop useful properties enhanced stability.27,28 thin layer hydrophobic coating surfaces vulnerable used humid environment. Owing low content, polymer-coated essentially retain all original MOFs.29,30 Similar cage-based ideal hosts polymerization.31 typically formed light- or heat-induced radical polymerization, first treated monomers then process initiated light heat. catalytically metal clusters exhibit strong chemical transformation32 polymerize monomers.33 We considered could catalyze monomers, afford highly stable interlocking scaffold secure framework. Novel Scheme 1 because mechanism, different incorporated. | introducing polyurea enhance stability. article, we describe hierarchically MSF-1). Upon removal molecules, MSF-1 completely collapsed For time, trinuclear Zr(IV) transformation isocyanate urea compounds. Furthermore, proceeded introduce mechanical support way, framework, retrofitted situ, becomes robust retains adsorption. Experimental Methods Synthesis trizirconium unit compound [Zr3(Cp)3O(OH)3(p-TBBA)3]·Cl (Zr-p-TBBA) p-tert-butyl benzoic acid p -TBBA; 50 mg, 0.28 mmol) zirconocene dichloride (Cp2ZrCl2; 86 0.29 dissolved mL tetrahydrofuran ultrasonication, chloroform (CHCl3) 100 μL H2O added, vial was capped placed at room temperature without disturbance, finally plate-like crystal 3 days. washed acetone twice dried air. 1H NMR [400 MHz, dimethyl sulfoxide (DMSO)-d6, 295 K]: δ = 10.39 (s, 3H, O- H), 7.80–7.82 (d, 6H, Ph- 7.38–7.40 6.63 15H, Cp- 1.19 27H, methyl- H). Elemental analysis: calcd (%) [Zr3(Cp)3O(OH)3(p-TBBA)3]+·Cl−, C 46.84, H 5.05; found (%), 47.04, 5.12. Infrared (IR) (KBr, cm−1): 3347, 1610, 1584, 1528, 1410, 1193, 1018, 813, 710, 622, 484. 2′,5′-Dimethyl-[1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic (H2DMTPDC; 20 0.06 Cp2ZrCl2 (40 0.14 2 N,N-dimethylacetamide (DMAc) 400 added. After mixture became via dichloromethane (DCM) subsequently ultrasonicated 5 min, heated 65 °C oven 8 h. mother liquid decanted immediately out oven, crystals DMAc times, 30 mg harvested (yield ∼73.6%). (400 DMSO-d6, K): 10.56 (br, 12H, 8.06 24H, 7.47 7.01 6.69 60H, 1.95 36H, CH3- Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) (DMSO): following selected signals those intensities. m/z [M–4Cl–2H)]2+, 2103.9824; found, 2103.9255; [M–4Cl–H]3+, 1402.6572; 1402.6189; [M–4Cl]4+, 1051.9945; 1051.9660. {[Cp3Zr3O(OH)3]4(DMTPDC)6}·Cl6·2Me2NH2·35H2O, 46.98, 5.42, N 0.53; 46.82, 4.24, 0.39. IR 3421, 1687, 1579, 1523, 1420, 617, 480. Synthetic conditions model reaction About 17 (0.02 1-hexyl (0.2 deuterated (CDCl3), stored (about °C) stirring day, analyzed NMR. Zr- -TBBA CDCl3, (0.016 as-synthesized exchanged times acetonitrile few CHCl3 During solvent exchange process, minimum amount submerge reserved avoid caused evaporation. fresh 1,6-hexamethylene diisocyanate (HDI) charged 10 vial. kept day. product soaking replaced DCM every 12 Results Discussion self-assembly linear H2DMTPDC ligand presence water afforded block-shaped crystals. Single X-ray diffraction revealed crystallized Fm-3m space group. analysis indicated isolated cationic coordination cage (Zr-DMTPDC) had (Figure 1). tetrahedral four vertices occupied cluster [Cp3Zr3O(OH)3]+ bridged six deprotonated DMTPDC ligands. composition confirmed high-resolution ESI-TOF-MS S4).34 charge balanced Cl− ions, play critical role high-order viewed building block connected eight adjacent ions charge-assisted O−H···Cl−···H−O hydrogen bond interactions, forming three-dimensional (3D) From topological perspective, aggregates consisting tetrahedron regarded 8- 4-connecting nodes, respectively. Thus, simplified (4,8)-connected 3D network fluorite flu) topology S5). Illustration MSF-1. Zr (brown), Cl (green), O (red), (purple). atoms omitted clarity. Remarkably, consists quasi-small rhombicuboctahedron, Archimedean triangular 18 square faces one 13 polyhedra derived inefficient Platonic A) diameter rhombicuboctahedron ∼27.30 Å (checked Zeo++ software), located range. penetrable open each tetrahedron. solvent-accessible volumes about 74.9%, estimated software35 structure data. phase purity bulk crystalline reliable match experimental simulated powder patterns (PXRD) 2a). morphology characterized field-emission scanning electron microscopy (FE-SEM) showed possesses regular cubic smooth 3a). (a) PXRD characterization (b) adsorption before treatment HDI. ads des abbreviations represent desorption, prompted investigation properties. area parameters activated sample, standard nitrogen 77 K, displays I isotherm characteristic microporous rather than IV typical N2 capacity approximately 198 cm3 g−1 bar 2b). Brunauer–Emmett–Teller (BET) area, calculated data, 561 m2 g−1. uptake BET much lower Zr-MOC-based samples sorption experienced loss amorphous 2a), indicating removal. common phenomenon lacking connectivity similar observed MOFs.36 increased bonding density underlie Table S2). reduction B) during resulted displaying capacity. ascribed reduced interstitial cages. FE-SEM images (a), (b), AcOH MeOH (c). Scale µm. effective means improve framework.27,28 envisioned might if (Scheme Isocyanates precursors nylon polyureas. Organometallic catalysts, including lanthanide complexes compounds, excellent activity insertion,37 cyclodimerization,38 cyclotrimerization isocyanates.39 materials, recently developed not isocyanates urea. view fact uniformly served centers, penetrative void mesopore transportation enrich reactants. speculate act catalyst fabrication. test feasibility speculation, performed using reactant. blank carried adding CDCl3 temperature. indicate no diagnostic peaks 4). When examined reaction, exhibited urea-CH2 urea-NH 3.14 4.60 ppm observed, demonstrating diffusion nature reaction. identified 13C spectra S6), compared published data.40 identify center representing formula synthesized S7) employed 43.5% substrate converted 1,3-dihexylurea solubility, preformed nonporous considerable activity. slight solubility verified spectroscopy, 6.86, 7.36, 7.85 ppm. these results, concluded responsible performance. 4 catalyzed p-TBBA Following success attempted establish replacing denoted protected], fluffy feature introduced. successful introduction cross-polarization magnetic angle spinning (CP-MAS) 5). addition MSF-1, 25, 39, 157 peak 39 broad 25 methylene groups, assigned urea-C polyurea.41,42 spectrum when employed, most easily diffused supported conclusion. N, C, contents HDI Peaks 2900 cm−1 Fourier-transform (FT-IR) correspond C–H vibration groups methyl group ligands construct S8). Thermal gravimetric (TGA) more significant weight polyurea-loaded sample S9). integrity FE-SEM. retained homogeneously coated layer, pristine 3b). literature,43 insoluble solvents. Solid isocyanate. K. I/IV mixed significantly 870 ∼2600 appears suggests inherent maintained, aperture window blocked polyurea. understand phenomenon, modified PXRD. difference EXPO2014 (Rietveld refinement refine nonstructural Le Bail method). result matched well data (Rp 5.754%, Rwp 7.442%, S10). indicates maintained Therefore, function structure. cover confirm this, distribution (PSD) nonlocal functional theory (NLDFT), three distinct pores sizes 0.63, 1.24, 2.46 nm S11). These values consistent according structure.23 PSD did deviate value further verify existence excess acetic methanol decompose frameworks. Cubic boxes directed obtained 3c), clearly polymerization. initially inhibited penetration subsequent 3c). hollow morphologies. raises possibility dense achieved. Although performance extended widely investigated44 display promising capabilities, especially storage remain unexplored they tend demonstrate isotherms collected 0 56 298 importance retention 6). reversible ∼186 (132 g−1), recorded frameworks.45 boost high-quality adsorbent improved usage efficiency. 6 High-pressure K protected]. Stabilization challenging larger porosity, but viability modify less HDI, diminished Figures S12 S13), cavity although incorporated inevitably reduces maximum achievable provides additional works prevent collapse. compromise search porosities sorption, conceivably generalized centers. Conclusions fabricating supporting scaffold. It series MSF-1s virtue compatibility carboxylic acids. broader platform application-oriented investigations. MOFs. Meanwhile, impart superior hydrophobicity. synergetic effects being explored laboratory. available. Conflict Interest There conflict interest report. 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