Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

 
 
Session Overview
Session
MS-20: Dynamic frameworks
Time:
Monday, 16/Aug/2021:
10:20am - 12:45pm

Session Chair: Christopher SUMBY
Session Chair: Michael John Zaworotko
Location: Club C

50 1st floor

Invited: Hoi Ri Moon (Republic of Korea), Yao Chen (China)


Session Abstract

Dynamic behaviour and structural flexibility are important properties of extended frameworks, such as Metal-organic Frameworks (MOFs), and in porous solids composed of molecular materials, like Metal-organic Polyhedra (MOPs) and Porous Organic Cages (POCs).  In extended materials this can be realised as breathing or stimulus-response, providing access to unexpected porosity or sensing behaviour.  For molecular materials, which lack strong bonding between components, structural transformations in response to sorbents can be profound, leading to advantageous sorption and separation processes. This session will examine the dynamic behaviour and structural flexibility of both molecular and extended porous frameworks, with a focus on phase transitions, which can be monitored by X-ray crystallography.

For all abstracts of the session as prepared for Acta Crystallographica see PDF in Introduction, or individual abstracts below.


Introduction
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Presentations
10:20am - 10:25am

Introduction to session

Christopher Sumby, Michael John Zaworotko



10:25am - 10:55am

Flexible Metal-Organic Frameworks for Hydrogen Isotope Separation

Hoi Ri Moon

Department of Chemistry, Ulsan National Institute of Science and Technology, Ulsan, Korea, Republic of (South Korea)

Rational and creative design of organic and metal building blocks has successfully enabled the genesis of a variety of coordination polymers or metal-organic frameworks (MOFs) that are of fundamental scientific importance as well as provide a myriad of practical applications including gas storage and separation, catalysis, and sensing. One of the most attractive features in MOFs is flexibility because they show distinctive properties that cannot be achieved with rigid MOFs and other porous inorganic materials. In this talk, we will present strategies that exploit flexible MOFs for effectively separating hydrogen isotopes through the dynamic pore change of flexible MOFs. Especially, a unique isotope-responsive breathing transition of the flexible MOF was studied, which selectively recognize and respond to only D2 molecules through a secondary breathing transition, monitored by in situ neutron diffraction experiments.

External Resource:
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10:55am - 11:25am

Novel composite platform: Biomolecules-incorporation for biocatalysis, separation and biopharmaceutical formulations

Yao Chen

Nankai University, Tianjin, China, People's Republic of

Biomacromolecules, such as enzymes, are ubiquitous in nature and essential for maintaining basic life activities. Apart from the fundamental biological functions, biomacromolecules are also of great values in industrial applications, especially in food and pharmaceutical production. However, their industrial applications are often handicapped by low operational stability, poor robustness, difficult recovery and reuse. Incorporation of biomolecules within protective exteriors has been proved to be an effective method to promote their stabilities and applications. As new classes of crystalline solid-state materials, porous frameworks materials (such as covalent-organic frameworks, COFs and metal-organic frameworks, MOFs) feature high surface area, tunable pore size, high stability, and easily tailored functionality, which entitle them as ideal supports for encapsulation of biomolecules to form novel composite materials for various applications. Moreover, the formed composites can combine the properties of both constitutes, where crystalline frameworks materials and biomolecules are indeed mutually beneficial. Our researches mainly focus on their biocatalysis, separation and medicinal applications. This novel crystalline platform composed of biomolecules-incorporation and framework materials exhibited various functionality and superior poteintials in biocatalysis, bioseparation, and biopharmaceutical formulations.

External Resource:
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11:25am - 11:45am

Dynamic frameworks: the role of non-covalent interactions

Susan Ann Bourne

University of Cape Town, Cape Town, South Africa

Supramolecular chemistry places focus on the weak non-covalent interactions between molecules in the solution or solid phases. These “soft” interactions are reversible and allow one to build materials which are responsive to their chemical or physical environment, changing form and properties under the influence of heat, light, pressure or chemical probes.

Dynamic materials, capable of responding to their environment, require flexibility which may be achieved using interactions such as hydrogen- or halogen-bonding or through the use of suitable metals and ligands in coordination compounds. Frameworks may be made up of relatively strongly bound entities such as those that make up metal-organic frameworks (MOFs) or may be more loosely bound such as host-guest systems where the host molecules crystallise as independent entities but leave spaces which can accommodate guest molecules. The process of guest exchange within porous solids can be used in a range of applications, such as selective absorption or separation of gases and heterogeneous catalysis. Among the more interesting examples of dynamic processes in frameworks are those which result in thermochromic and/or mechanochromic effects. Materials of this type are particularly of interest if they are able to revert to their original state on application of another external perturbation signal. Rational design of such systems remains a challenge however, and is thus an exciting area for application of crystal engineering principles.

In this presentation, examples from recent work in our laboratory will be presented, including MOFs and 3D hydrogen bonded frameworks constructed from the same flexible ditopic ligands. The influence of halogen versus hydrogen bonding on a molecular host-guest system will also be described. Frameworks exhibit thermochromic and mechanochromic properties, depending on the application of external stimuli such as heat, grinding or exposure to solvent vapours. Further examples will include the selective inclusion of halogenated volatile organic compounds in a porous metal-organic framework (Fig. 1).

External Resource:
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11:45am - 12:05pm

Synthesis and structural properties of isostructural Zn(II) M12L8 poly-[n]-catenane using the 2,4,6-tris(4-pyridyl)benzene (TPB) ligand

Javier Marti-Rujas, Stefano Torresi, Antonino Famulari

Politecnico di Milano, Milan, Italy

The use of mechanical bonds for the synthesis of catenanes is a challenging process because of the many factors controlling the interpenetration process.[1,2] We report the kinetic control in the presence of various aromatic solvents of a poly-[n]-catenane (1). The polymeric structure is composed of interlocked M12L8 icosahedral nanometric cages with internal voids of ca. 2500 Å3.[3] Using the symmetric exotridentate tris-pyridyl benzene (TPB) ligand and ZnCl2 with appropriate templating solvent molecules due to the good ligand aromatic interactions are used, the metal-organic nanocages can be synthesized very fast, homogeneously, and in large amounts as microcrystals (Figure 1). Synchrotron single-crystal X-ray data (100 K) allowed the resolution of nitrobenzene guest molecules at the internal walls of the M12L8 cages, while in the centre of the nanocages the solvent is disordered and not observable by X-ray diffraction data. The guest release occurs in two steps with the disordered nitrobenzene released in the first step (lower temperatures) because of the lack of strong cage-guest interactions. Solid-state quantum mechanics provided a rationalization of the results, in particular, solid-state approaches, showed theoretical evidence of the kinetic nature in the formation of the polycatenation of the M12L8 nanocages by the analysis of the packing energy considering monomeric and dimeric cages.

Figure 1. Synthesis of the M12L8 interlocked nanocages forming the poly-[n]-catenane 1 under aromatic control.

[1] J. F. Stoddart (2009). Chem. Soc. Rev. 38, 1802-1820.

[2] Frank, M., Johnstone, M. D. & Clever, G. (2016). Chem.- Eur. J. 22, 14104-14125.

[3] Torresi, S., Famulari, A. & Martí-Rujas, J. (2020). J. Am. Chem. Soc. 142, 9537-9543.

External Resource:
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12:05pm - 12:25pm

Cocrystallization, high pressure/low temperature behaviour and vapochromism in a family of aurophilic copper-gold supramolecular networks.

Emanuele Priola1, Nadia Curetti2, Domenica Marabello1, Jacopo Andreo3, Alessia Giordana1, Lorenza Operti1, Piera Benna2, Eliano Diana1

1Department of Chemistry, Università di Torino, Via Pietro Giuria 7, 10125 Torino, Italy; 2Department of Earth sciences, University of Torino, Via Valperga Caluso 35, 10125, Turin, Italy; 33Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Viale G. P. Usberti 17A, 43100 Parma, Italy

The synthesis and conception of coordination polymers and supramolecular networks based on gold(I) complexes used as metallo-ligands (especially dicyanoaurate) is an established procedure to obtain materials with exciting properties: phosphorescence, non-linear optical behaviour, vapochromism and non-classical response to temperature and pressure [1-2]. However, the appearance of these solid-state properties is often connected to the manifestation of aurophilic interaction. The Au(I)‧‧‧Au(I) interaction, an attraction between closed shell d10 metal centres, is a relativistic effect that has a strength comparable to that of classical hydrogen bond [3]. Therefore, the study of new functional materials based on gold(I) properties must encourage the formation of these contacts in the crystal environment. We prepared, by a judicious choice of chelating ligands and balance in coordination equilibria [4], a series of 12 new coordination polymers or supramolecular networks based on dicyanoaurate anion and copper complexes presenting aurophilic interactions. The choice of copper as metal centre to connect to [Au(CN)2]- makes the synthesis particularly predictable due to the Jahn-Teller effect in the case of Cu(II), and the appearance of Cu(I) compounds due to redox effect of specific ligands will be commented. These compounds have been tested for vapochromism, and their behaviour in presence of ammonia has been interpreted with Raman, Ir and Uv-Vis absorption spectroscopy. On the same time, the response to temperature (T= 100-420 K) and pressure (P= 0.1-1.5 GPa) of {Cu(bipy)2[Au(CN)2]}[Au(CN)2] (bipy =2,2’-bipyridine), a prototypical bimetallic aurophilic supramolecular network, has been investigated. Both the dependence of structural and reticular parameters to thermal and compression stimuli has been studied, and a phase transition at 1.2 GPa has been revealed. Moreover, we investigated the possibility to modulate the structural behaviour with the cocrystallization with other d10 metal tectons, and we demonstrate the possibility to obtain inclusion compounds with the presence of Hg(CN)2 with a 3D weakly interacting framework still presenting Au‧‧‧Au contacts.

External Resource:
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12:25pm - 12:45pm

Structural modifications occurring during the water sorption processes on a potential material for autonomous indoor humidity control

Patrice Kenfack Tsobnang1, Thiery Yannick Sakam Nchedoung1, Dominik Fröhlich2, Emrah Hastürk3, Florence Porcher4, Christoph Janiak3

1University of Dschang, Department of Chemistry, PO Box 67, Dschang, Cameroon; 2Fraunhofer-Institut for Solar Energy Systems ISE, Division Thermal Systems and Buildings, Heidenhofstraße 2, 79110 Freiburg, Germany; 3Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany; 4Laboratoire Léon Brillouin (LLB), UMR 12 CEA/CNRS, Bât. 563 CEA Saclay, 91191 Gif-sur-Yvette cedex, France

The supramolecular compound catena-{[Co(amp)3][Cr(C2O4)3]·6H2O}(I) was synthetized as reported earlier [1,2]. To get insight into the structural modifications of its architecture within the water sorption processes (see Fig.1 (a)), in situ powder X-Ray Diffraction (PXRD) measurements were performed on a Bruker D8 Advance Diffractometer in a Bragg−Brentano geometry, using Cu(Kα1) radiation. The humidity was controlled by exposing the sample to a nitrogen flow heated at 40°C and having humidity rates ranging from 0 to 90% relative humidity (r.H.) and then from 90 to 0% r.H. The PXRD carpet plot diagram ((see Fig.1 (b)) and the refinements of the PXRD patterns coupled with the single crystal diffraction results were used. During the adsorption and desorption processes, only two phases are involved, that of the dehydrated phase ([Co(amp)3][Cr(C2O4)3] (I’), P 21/n, a= 12.0542, b=16.0920, c = 13.8841, β = 99.8013) and the hydrated phase (I, P 21/n; a= 13.2330, b=18.2611, c = 14.1396, β = 100.5016). For the adsorption process, during the first step (from 0 to 30% r.H) corresponding to an adsorption of ∼ 1 mol H2O / mol of I’, only phase I’ is involved and the volume of its unit cell does not change significantly. During the second step (from 30 to 35% r.H.) corresponding to an abrupt adsorption of ∼5.6 mol H2O / mol of I’, both phases are involved with different percentages (deduced from Rietveld refinements) progressing to the complete conversion of I’ to I. During the third phase where the quantity of water adsorbed shows a plateau (from 35 to 90 % r.H.), only phase I is present and the volume of its unit cell does not change significantly with the humidity. For the desorption process, the same observations apply. During the first step (from 90 to 20 % r.H.) only I is present and its volume decreases just slightly. During the deep desorption process (from 20 to 14 % r.H.), both phases are involved with different percentages and during the last step (from 14 to 0% r.H) at the contrary to the adsorption process, both phases are still present while the sorption isotherm in this region looks like a type-I isotherm in the IUPAC classification [4]. These results suggest a quick capillary condensation followed by a pore filling process that produces a type-V isotherm profile [4], in relation with the first order structural transition followed by insignificant changes of the unit cell volume. The adsorption and desorption branches in the S- shaped isotherms of H2O-vapor for this compound occur at the values of relative humidity at which these phase transitions start. The conversion of I to I’ and vis-versa is followed by the cleavage and formation of the hydrogen bonds in the architectures of these materials.

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