Neil B. McKeown

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Organization: University of Edinburgh , England

Department: School of Chemistry

Title: (PhD)

TOPICS

Organic Chemistry

Organocatalysis TRIPTYCENE

Chemicals
References

The synthesis of polymers of intrinsic microporosity (PIMs)

Co-reporter:Neil B. McKeown

Science China Chemistry 2017 Volume 60( Issue 8) pp:1023-1032

Publication Date(Web):04 July 2017

DOI:10.1007/s11426-017-9058-x

Polymers of intrinsic microporosity (PIMs) are a class of porous organic polymer (POP) that form microporous solids due to the inefficient packing of their rigid and contorted macromolecular chains. In contrast to other types of POP, PIMs are not comprised of a network of cross-linked covalent bonds so that they can be dissolved in organic solvents and processed into robust films, coatings or fibres. Here, over twelve years’ accumulated research on the synthesis of PIMs is reviewed. To date, three types of polymerisation reaction have been used successfully to prepare PIMs of sufficient molecular mass to form robust self-standing films. These involve the formation of dibenzodioxin, Tröger’s base and imide linkages between monomeric units. This rapid development of synthetic methods for preparing PIMs has been driven by their rich potential for numerous diverse applications and this synergistic relationship between synthesis and functionality is set to continue.

Polymers of Intrinsic Microporosity derived from a carbocyclic analogue of Tröger's base

Co-reporter:Mariolino Carta, C. Grazia Bezzu, James Vile, Benson M. Kariuki, Neil B. McKeown

Polymer 2017 Volume 126(Volume 126) pp:

Publication Date(Web):22 September 2017

DOI:10.1016/j.polymer.2017.03.037

•Polymers were prepared using a carbocyclic analogue of Tröger's base (TB).•Nitrogen adsorption showed that the polymers have modest intrinsic microporosity.•The carbocyclic analogue of generates a similar amount of microporosity as TB.•Without bulky substituents both TB and its analogue produce insoluble polymers.Tröger's base (TB) is often used as a building block for the synthesis of Polymers of Intrinsic Microporosity (PIMs) due to its rigid bicyclic V-shaped structure. In this study the TB component in the structure of a PIM is replaced by 2,3:6,7-dibenzobicyclo[3.3.1]nonane, a purely carbocyclic analogue of TB. This modification results in only a slightly reduced amount of microporosity as determined using nitrogen adsorption. Further comparisons with previously reported PIMs indicate that this building unit (and therefore TB) is significantly less effective for the generation of intrinsic microporosity than spirobisindane, a commonly used structural unit for PIM synthesis. It appears that the V-shape of the 2,3:6,7-dibenzobicyclo[3.3.1]nonane and TB units allows closer contact between polymer chains thereby enhancing packing efficiency.Download high-res image (147KB)Download full-size image

Synthesis, crystallographic characterization and homogeneous catalytic activity of novel unsymmetric porphyrins

Co-reporter:A. R. Antonangelo;K. C. M. Westrup;L. A. Burt;C. Grazia Bezzu;T. Malewschik;G. S. Machado;F. S. Nunes;N. B. McKeown;S. Nakagaki

RSC Advances (2011-Present) 2017 vol. 7(Issue 80) pp:50610-50618

Publication Date(Web):2017/10/30

DOI:10.1039/C7RA08734A

Unsymmetric porphyrins, containing both pentafluorophenyl (PFP = A) and 3,4-dimethoxyphenyl (DMP = B) substituents at the meso positions, were prepared using Lindsey's methodology. The isomeric trans-A2B2 (P1) and cis-A2B2 (P2) porphyrins together with the tris(pentafluorophenyl)porphyrin A3B (P3) were isolated using chromatography. The porphyrins were characterized by UV-VIS, 1H NMR spectroscopy, mass spectrometry, elemental analysis (C, H, N) and cyclic voltammetry (CV), and their molecular structures were confirmed by single crystal XRD. Their manganese complexes, MnP1, MnP2 and MnP3, were also synthesised and used as catalysts in cyclooctene and cyclohexane oxidation reactions under homogeneous conditions. The catalytic studies were supported by electrochemical measurements and showed that the number of electron-withdrawing substituents on the porphyrins rings influences the catalytic activity. These porphyrins may be used as precursors for the design of new materials, such as Polymers of Intrinsic Microporosity (PIMs).

Inexpensive polyphenylene network polymers with enhanced microporosity

Co-reporter:Kadhum J. Msayib and Neil B. McKeown

Journal of Materials Chemistry A 2016 vol. 4(Issue 26) pp:10110-10113

Publication Date(Web):17 Jun 2016

DOI:10.1039/C6TA03257E

Greatly enhanced microporosity is obtained for the amorphous porous polymers produced from the AlCl3-mediated coupling of aromatic hydrocarbons by using dichloromethane as the reaction solvent. A polymer of average BET surface area = 2435 m2 g−1 was obtained reproducibly from 1,3,5-triphenylbenzene with the additional porosity being provided as ultramicroporosity as demonstrated by very high CO2 adsorption at 273 K/1 bar.

Enhancing the Gas Permeability of Tröger’s Base Derived Polyimides of Intrinsic Microporosity

Co-reporter:Michael Lee, C. Grazia Bezzu, Mariolino Carta, Paola Bernardo, Gabriele Clarizia, Johannes C. Jansen, and Neil B. McKeown

Macromolecules 2016 Volume 49(Issue 11) pp:4147-4154

Publication Date(Web):May 24, 2016

DOI:10.1021/acs.macromol.6b00351

A series of four novel Tröger’s base (TB) derived polyimides of intrinsic microporosity (PIM–TB–PI) is reported. The TB diamine monomer (4MTBDA) possesses four methyl groups in order to restrict rotation about the C–N imide bonds in the resulting polymers. The polymers possess apparent BET (Brunauer, Emmett, and Teller) surface areas between 584 and 739 m2 g–1, complete solubility in chloroform, excellent molecular mass, high inherent viscosity and good film-forming properties. Gas permeability measurements demonstrate enhanced performance over previously reported polyimide-based Tröger’s base (TB) polymers confirming the benefit of the additional methyl groups within the TB diamine monomer. Notably, a polyimide derived from 4MTBDA and pyromellitic anhydride (PMDA) demonstrates gas permeability data above the 2008 upper bounds for important gas pairs such as O2/N2, H2/N2, and H2/CH4.

The Synthesis of Organic Molecules of Intrinsic Microporosity Designed to Frustrate Efficient Molecular Packing

Co-reporter:Dr. Rupert G. D. Taylor;Dr. C. Grazia Bezzu;Dr. Mariolino Carta;Dr. Kadhum J. Msayib;Dr. Jonathan Walker;Dr. Rhys Short;Dr. Benson M. Kariuki; Neil B. McKeown

Chemistry - A European Journal 2016 Volume 22( Issue 7) pp:2466-2472

Publication Date(Web):

DOI:10.1002/chem.201504212

Abstract

Efficient reactions between fluorine-functionalised biphenyl and terphenyl derivatives with catechol-functionalised terminal groups provide a route to large, discrete organic molecules of intrinsic microporosity (OMIMs) that provide porous solids solely by their inefficient packing. By altering the size and substituent bulk of the terminal groups, a number of soluble compounds with apparent BET surface areas in excess of 600 m² g⁻¹ are produced. The efficiency of OMIM structural units for generating microporosity is in the order: propellane>triptycene>hexaphenylbenzene>spirobifluorene>naphthyl=phenyl. The introduction of bulky hydrocarbon substituents significantly enhances microporosity by further reducing packing efficiency. These results are consistent with findings from previously reported packing simulation studies. The introduction of methyl groups at the bridgehead position of triptycene units reduces intrinsic microporosity. This is presumably due to their internal position within the OMIM structure so that they occupy space, but unlike peripheral substituents they do not contribute to the generation of free volume by inefficient packing.

Highly Permeable Benzotriptycene-Based Polymer of Intrinsic Microporosity

Co-reporter:Ian Rose, Mariolino Carta, Richard Malpass-Evans, Maria-Chiara Ferrari, Paola Bernardo, Gabriele Clarizia, Johannes C. Jansen, and Neil B. McKeown

ACS Macro Letters 2015 Volume 4(Issue 9) pp:912

Publication Date(Web):August 13, 2015

DOI:10.1021/acsmacrolett.5b00439

A novel polymer of intrinsic microporosity (PIM) was prepared from a diaminobenzotriptycene monomer using a polymerization reaction based on Tröger’s base formation. The polymer (PIM-BTrip-TB) demonstrated an apparent Brunauer, Emmet, and Teller (BET) surface area of 870 m2 g–1, good solubility in chloroform, excellent molecular mass, high inherent viscosity and provided robust thin films for gas permeability measurements. The polymer is highly permeable (e.g., PH2 = 9980; PO2 = 3290 Barrer) with moderate selectivity (e.g., PH2/PN2 = 11.0; PO2/PN2 = 3.6) so that its data lie over the 2008 Robeson upper bounds for the H2/N2, O2/N2, and H2/CH4 gas pairs and on the upper bound for CO2/CH4. On aging, the polymer demonstrates a drop in permeability, which is typical for ultrapermeable polymers, but with a significant increase in gas selectivities (e.g., PO2 = 1170 Barrer; PO2/PN2 = 5.4).

Triptycene Induced Enhancement of Membrane Gas Selectivity for Microporous Trger's Base Polymers

Co-reporter:Mariolino Carta;Matthew Croad;Richard Malpass-Evans;Johannes C. Jansen;Paola Bernardo;Gabriele Clarizia;Karel Friess;Marek Lan&x10d;

Advanced Materials 2014 Volume 26( Issue 21) pp:3526-3531

Publication Date(Web):

DOI:10.1002/adma.201305783

A highly permeable polyimide with enhanced selectivity for membrane gas separations

Co-reporter:Yulia Rogan, Richard Malpass-Evans, Mariolino Carta, Michael Lee, Johannes C. Jansen, Paola Bernardo, Gabriele Clarizia, Elena Tocci, Karel Friess, Marek Lanč and Neil B. McKeown

Journal of Materials Chemistry A 2014 vol. 2(Issue 14) pp:4874-4877

Publication Date(Web):20 Feb 2014

DOI:10.1039/C4TA00564C

A highly gas permeable polyimide with improved molecular sieving properties is produced by using a bisanhydride monomer based on the rigid ethanoanthracene unit. The polymer (PIM-PI-EA) demonstrates enhanced selectivity for gas separations so that its gas permeability data lie above the 2008 Robeson upper bounds for the important O2–N2, H2–N2, CO2–CH4 and CO2–N2 gas pairs.

Triptycene-Based Organic Molecules of Intrinsic Microporosity

Co-reporter:Rupert G. D. Taylor, Mariolino Carta, C. Grazia Bezzu, Jonathan Walker, Kadhum J. Msayib, Benson M. Kariuki, and Neil B. McKeown

Organic Letters 2014 Volume 16(Issue 7) pp:1848-1851

Publication Date(Web):March 17, 2014

DOI:10.1021/ol500591q

Four Organic Molecules of Intrinsic Microporosity (OMIMs) were prepared by fusing triptycene-based components to a biphenyl core. Due to their rigid molecular structures that cannot pack space efficiently, these OMIMs form amorphous materials with significant microporosity as demonstrated by apparent BET surface areas in the range of 515–702 m2 g–1. Bulky cyclic 1′,2′,3′,4′-tetrahydro-1′,1′,4′,4′-tetramethylbenzo units placed on the triptycene termini are especially efficient at enhancing microporosity.

The synthesis of microporous polymers using Tröger's base formation

Co-reporter:Mariolino Carta, Richard Malpass-Evans, Matthew Croad, Yulia Rogan, Michael Lee, Ian Rose and Neil B. McKeown

Polymer Chemistry 2014 vol. 5(Issue 18) pp:5267-5272

Publication Date(Web):20 Jun 2014

DOI:10.1039/C4PY00609G

A step-growth polymerisation based on the formation of Tröger's base, performed by simple reaction of a suitable aromatic diamine monomer with dimethoxymethane in trifluoroacetic acid, provides polymers of high average molecular mass. The properties of the resulting polymers can be tailored by the choice of monomer. In particular, the Tröger's base polymerisation is highly suited to the preparation of soluble polymers of intrinsic microporosity (PIMs) due to the resulting fused-ring TB linking group, which is both highly rigid and prohibits conformational freedom.

Heterogeneous organocatalysts composed of microporous polymer networks assembled by Tröger's base formation

Co-reporter:Mariolino Carta, Matthew Croad, Keith Bugler, Kadhum J. Msayib and Neil B. McKeown

Polymer Chemistry 2014 vol. 5(Issue 18) pp:5262-5266

Publication Date(Web):20 Jun 2014

DOI:10.1039/C4PY00608A

Microporous polymer networks are assembled from triamino-triptycene monomers using a polymerisation reaction based on the formation of Tröger's base (TB). The highly rigid triptycene units ensure that the polymer networks demonstrate significant intrinsic microporosity as demonstrated by apparent surface areas of up to 1000 m2 g−1. These networks act as heterogeneous basic catalysts which enhance greatly the rate of a model Knovenagel reaction between malonontrile and benzaldehyde. Indeed, the microporous networks, which possess a high concentration of basic sites, enhance the rate of the Knovenagel reaction even more efficiently than using Tröger's base as a homogeneous catalyst.

Synthesis of cardo-polymers using Tröger's base formation

Co-reporter:Mariolino Carta, Matthew Croad, Johannes C. Jansen, Paola Bernardo, Gabriele Clarizia and Neil B. McKeown

Polymer Chemistry 2014 vol. 5(Issue 18) pp:5255-5261

Publication Date(Web):20 Jun 2014

DOI:10.1039/C4PY00607K

A series of novel cardo-polymers was prepared using a polymerisation reaction based on Tröger's base formation. The precursor dianiline monomers are readily available from the reactions between appropriate anilines and cyclic ketones. One adamantyl-based cardo-polymer displays intrinsic microporosity with an apparent BET surface area of 615 m2 g−1. This polymer demonstrates a combination of good solubility and high molecular mass facilitating the solvent casting of robust films suitable for gas permeability measurements. The intrinsic microporosity of the polymer provides high gas permeabilities and moderate selectivities with particular promise for gas separations involving hydrogen.

Gas Permeability of Hexaphenylbenzene Based Polymers of Intrinsic Microporosity

Co-reporter:Mariolino Carta, Paola Bernardo, Gabriele Clarizia, Johannes C. Jansen, and Neil B. McKeown

Macromolecules 2014 Volume 47(Issue 23) pp:8320-8327

Publication Date(Web):November 21, 2014

DOI:10.1021/ma501925j

The synthesis and characterization of a series of novel hexaphenylbenzene (HPB) based polymers of intrinsic microporosity (PIM-HPBs) containing methyl, bromine, and nitrile substituents are reported. The successful formation of thin films from these polymers allowed the evaluation of the influence of the substituents on intrinsic microporosity and gas permeability. Analysis by the time-lag method also yielded information about gas diffusion coefficients and, indirectly, the gas solubility. The gas permeability varies as a function of the polarity of the substituents and shows a significant increase after treatment of the samples with methanol, especially for films cast from THF as the solvent. This enhancement, which is mostly due to an increase in the diffusion coefficient, is only partially lost upon aging of the membranes for 5 months. Measurements at different feed pressures confirm the typical dual mode sorption behavior, with increasing diffusivity and decreasing permeability and solubility as a function of the feed pressure.

Metastable Ionic Diodes Derived from an Amine-Based Polymer of Intrinsic Microporosity

Co-reporter:Dr. Elena Madrid;Yuanyang Rong;Dr. Mariolino Carta; Neil B. McKeown;Richard Malpass-Evans; Gary A. Attard;Tomos J. Clarke; Stuart H. Taylor; Yi-Tao Long; Frank Marken

Angewandte Chemie International Edition 2014 Volume 53( Issue 40) pp:10751-10754

Publication Date(Web):

DOI:10.1002/anie.201405755

Abstract

A highly rigid amine-based polymer of intrinsic microporosity (PIM), prepared by a polymerization reaction involving the formation of Tröger’s base, is demonstrated to act as an ionic diode with electrolyte-dependent bistable switchable states.

Metastable Ionic Diodes Derived from an Amine-Based Polymer of Intrinsic Microporosity

Co-reporter:Dr. Elena Madrid;Yuanyang Rong;Dr. Mariolino Carta; Neil B. McKeown;Richard Malpass-Evans; Gary A. Attard;Tomos J. Clarke; Stuart H. Taylor; Yi-Tao Long; Frank Marken

Angewandte Chemie 2014 Volume 126( Issue 40) pp:10927-10930

Publication Date(Web):

DOI:10.1002/ange.201405755

Abstract

Inexpensive polyphenylene network polymers with enhanced microporosity

Co-reporter:Kadhum J. Msayib and Neil B. McKeown

Journal of Materials Chemistry A 2016 - vol. 4(Issue 26) pp:NaN10113-10113

Publication Date(Web):2016/06/17

DOI:10.1039/C6TA03257E

A highly permeable polyimide with enhanced selectivity for membrane gas separations

Co-reporter:Yulia Rogan, Richard Malpass-Evans, Mariolino Carta, Michael Lee, Johannes C. Jansen, Paola Bernardo, Gabriele Clarizia, Elena Tocci, Karel Friess, Marek Lanč and Neil B. McKeown

Journal of Materials Chemistry A 2014 - vol. 2(Issue 14) pp:NaN4877-4877

Publication Date(Web):2014/02/20

DOI:10.1039/C4TA00564C