The adsorption behavior of xylene isomers in MIL-47 from a theoretical perspective

Recently, the spectrum of nanoporous materials like zeolites and zeotype structures was further expanded through the occurrence of a new class of hybrid porous porous solids [1, 2]. Those materials are nowadays also known as metal organic frameworks or MOFs and consist of inorganic and organic moieties. Certain MOFs exhibit a very interesting adsorption and even catalytic behavior. Our study focuses on one of them: MIL-47. MIL-47 was first synthesized by Barthelet [3], later on Alaerts [4] studied the ability of MIL-47 to separate several xylene isomers. This separation behavior of MIL-47 could be better understood with adsorption studies [4, 5]. The adsorbates were located inside the MIL-47 host by Rietveld refinements of the XRD patterns of MIL-47 samples saturated with each of the C8-isomers. The packing of each C8-pair was then discussed on the basis of the interactions between those two aromatic compounds and MIL-47 [4]. In this case, theoretical modeling could predict the relative energy difference between several possible geometries. The stability of a unit cell of MIL-47 fully loaded with four adsorbates was investigated with periodic calculations. Starting form crystallographic information (supp. info of [4]), two possible geometries were cut out for different C8-isomers: para-xylene, meta-xylene, ortho-xylene and ethylbenzene. The optimized structures are displayed in the figure below. The relative energy differences are shown relative to meta-xylene (II), the most unstable structure. [1] Ferey, G., Chemical Society Reviews 37 (2008) 191. [2] Tranchemontagne, D.J.L. , M. O'Keeffe, Z. Ni and Yaghi O.M., Angewandte Chemie-International Edition 47 (2008) 5136. [3] Barthelet, K., Marrot, J., Riou, D. and Ferey G. Angewandte Chemie-International Edition 41 (2002) 281. [4] Alaerts, L., Kirschhock, C.E.A., Maes, M., van der Veen, M.A., Finsy, V., Depla, A., Martens, J.A., Baron, G.V., Jacobs, P.A., Denayer, J.E.M. and De Vos, D.E. Angewandte Chemie-International Edition 46 (2007) 4293. [5] Finsy,V., Verelst, H., Alaerts, L., De Vos, D., Jacobs, P.A., Baron, G.V. and Denayer J.F.M. Journal of the American Chemical Society 130 (2008) 7110

Insights on the adsorption behavior of aromatics in MIL-47 and MIL-53 from a theoretical perspective

Recently, the spectrum of nanoporous materials like zeolites and zeotype structures has been further expanded through the discovery of a new class of hybrid porous solids [1, 2]. Those materials, nowadays also known as metal organic frameworks or MOFs, consist of both inorganic and organic moieties. Certain MOFs exhibit a very interesting adsorption and even catalytic behavior. Within this contribution, we will mainly focus on adsorption and separation of aromatic species in MIL-47 and MIL-53 [3, 4, 5]. Some of the presenting authors reported for first time on the successful use of MOFs as selective adsorbents for the extremely difficult and industrially relevant separations of para-xylene versus meta-xylene and para-xylene versus ethylbenzene [3]. Their study focuses on the MIL-47, which was first synthesized by Barthelet [4]. This separation behavior of MIL-47 could be better understood with adsorption studies [3, 5]. The packing of each C8-pair will be discussed on the basis of the interactions between those two aromatic compounds and MIL-47 [3]. In order to unravel the interaction between the guest molecules and the lattice, periodic Density Functional Theory calculations have been conducted. The DFT calculations were corrected for dispersion interaction [6] to include the long-range attractive forces. It seems that pi-pi stacking energies between pairs of aromatics but also with the walls of the MOF are crucial for the packing behavior in the pores

Circular economy indicators : what do they measure?

Circular Economy (CE) is a growing topic, especially in the European Union, that promotes the responsible and cyclical use of resources possibly contributing to sustainable development. CE is an umbrella concept incorporating different meanings. Despite the unclear concept, CE is turned into defined action plans supported by specific indicators. To understand what indicators used in CE measure specifically, we propose a classification framework to categorise indicators according to reasoning on what (CE strategies) and how (measurement scope), Despite different types, CE strategies can be grouped according to their attempt to preserve functions, products, components, materials, or embodied energy; additionally, indicators can measure the linear economy as a reference scenario. The measurement scope shows how indicators account for technological cycles with or without a Life Cycle Thinking (LCT) approach; or their effects on environmental, social, or economic dimensions. To illustrate the classification framework, we selected quantitative micro scale indicators from literature and macro scale indicators from the European Union 'CE monitoring framework'. The framework illustration shows that most of the indicators focus on the preservation of materials, with strategies such as recycling. However, micro scale indicators can also focus on other CE strategies considering LCT approach, while the European indicators mostly account for materials often without taking LCT into account. Furthermore, none of the available indicators can assess the preservation of functions instead of products, with strategies such as sharing platforms, schemes for product redundancy, or multifunctionality. Finally, the framework illustration suggests that a set of indicators should be used to assess CE instead of a single indicator

The resting membrane potential of hSC-CM in a syncytium is more hyperpolarised than that of isolated cells

Human-induced pluripotent stem cell (hiPSC) and stem cell (hSC) derived cardiomyocytes (CM) are gaining popularity as in vitro model for cardiology and pharmacology studies. A remaining flaw of these cells, as shown by single-cell electrophysiological characterization, is a more depolarized resting membrane potential (RMP) compared to native CM. Most reports attribute this to a lower expression of the Kir2.1 potassium channel that generates the I-K1 current. However, most RMP recordings are obtained from isolated hSC/hiPSC-CMs whereas in a more native setting these cells are interconnected with neighboring cells by connexin-based gap junctions, forming a syncytium. Hereby, these cells are electrically connected and the total pool of I-K1 increases. Therefore, the input resistance (Ri) of interconnected cells is lower than that of isolated cells. During patch clamp experiments pipettes need to be well attached or sealed to the cell, which is reflected in the seal resistance (Rs), because a nonspecific ionic current can leak through this pipette-cell contact or seal and balance out small currents within the cell such as I-K1. By recording the action potential of isolated hSC-CMs and that of hSC-CMs cultured in small monolayers, we show that the RMP of hSC-CMs in monolayer is approximately -20 mV more hyperpolarized compared to isolated cells. Accordingly, adding carbenoxolone, a connexin channel blocker, isolates the cell that is patch clamped from its neighboring cells of the monolayer and depolarizes the RMP. The presented data show that the recorded RMP of hSC-CMs in a syncytium is more negative than that determined from isolated hSC/hiPSC-CMs, most likely because the active pool of Kir2.1 channels increased

Candidate gene resequencing in a large bicuspid aortic valve-associated thoracic aortic aneurysm cohort: SMAD6 as an important contributor

Bicuspid aortic valve (BAV) is the most common congenital heart defect. Although many BAV patients remain asymptomatic, at least 20% develop thoracic aortic aneurysm (TAA). Historically, BAV-related TAA was considered as a hemodynamic consequence of the valve defect. Multiple lines of evidence currently suggest that genetic determinants contribute to the pathogenesis of both BAV and TAA in affected individuals. Despite high heritability, only very few genes have been linked to BAV or BAV/TAA, such as NOTCH1, SMAD6, and MAT2A. Moreover, they only explain a minority of patients. Other candidate genes have been suggested based on the presence of BAV in knockout mouse models (e.g., GATA5, NOS3) or in syndromic (e.g., TGFBR1/2, TGFB2/3) or non-syndromic (e.g., ACTA2) TAA forms. We hypothesized that rare genetic variants in these genes may be enriched in patients presenting with both BAV and TAA. We performed targeted resequencing of 22 candidate genes using Haloplex target enrichment in a strictly defined BAV/TAA cohort (n = 441; BAV in addition to an aortic root or ascendens diameter = 4.0 cm in adults, or a Z-score = 3 in children) and in a collection of healthy controls with normal echocardiographic evaluation (n = 183). After additional burden analysis against the Exome Aggregation Consortium database, the strongest candidate susceptibility gene was SMAD6 (p = 0.002), with 2.5% (n = 11) of BAV/TAA patients harboring causal variants, including two nonsense, one in-frame deletion and two frameshift mutations. All six missense mutations were located in the functionally important MH1 and MH2 domains. In conclusion, we report a significant contribution of SMAD6 mutations to the etiology of the BAV/TAA phenotype

Application of metal-organic frameworks in catalysis and adsorption

Metaal-organische netwerken (metal-organic frameworks, MOFs) zijn een nieuwe groep microporeuse en kristallijne materialen met bijzonder hoge porievolumes en een hoofdzakelijk organische poriebekleding. Momenteel ligt de nadruk in de literatuur nog sterk op de synthese van nieuwe materialen, terwijl de zoektocht naar toepassingen voor deze materialen nog maar net gestart is. Een veelbelovende toepassing voor MOFs is de opslag van waterstofgas als toekomstige brandstof in de automobielindustrie. De kennis van hun katalytische en adsorptieve eigenschappen in de vloeistoffase is echter eerder fragmentarisch. In deze thesis wordt de toepasbaarheid van MOFs voor katalyse en voor adsorptie vanuit de vloeistoffase onderzocht. Eerst wordt het katalytisch potentieel van [Cu3(BTC)2] bestudeerd. Dit MOF is opgebouwd uit CuII en benzeen-1,3,5-tricarboxylzuur (BTC); de Cu-sites zijn vrij toegankelijk. Het is een zeer selectieve katalysator voor isomerisaties van terpeenderivaten, zoals de omlegging van α-pineenoxide tot camfoleenaldehyde en de cyclisatie van citronellal tot isopulegol. Met [Cu3(BTC)2] als katalysator worden beide reacties gekatalyseerd met gelijkaardige of hogere opbrengsten in vergelijking met een reeks homogene referentiekatalysatoren. De stabiliteit, de herbruikbaarheid en het heterogeen karakter van [Cu3(BTC)2] worden kritisch bestudeerd. Verlies van Cu uit het rooster treedt niet op, maar er worden afzettingen van reactieproducten in de poriën gevormd. In de omvorming van het ethyleenketal van 2-bromopropiofenon, een reactie van belang voor de aanmaak van ontstekingswerende middelen, wordt het gewenste product bekomen met een opbrengst van 70%. [Cu3(BTC)2] kan ook gebruikt worden voor Diels-Alderreacties. Op basis van de productverdelingen bekomen in deze vier reacties kunnen de CuII sites geïdentificeerd worden als hard Lewiszure sites en wordt de afwezigheid van Brönstedzuurheid aangetoond. Deze resultaten worden bevestigd met een specifieke karakterisatietechniek die gebruik maakt van infraroodspectroscopie op geadsorbeerd CO en acetonitril. De hier ontwikkelde methode, die berust op een combinatie van katalytische testreacties en infraroodspectroscopie, is nuttig om de toepasbaarheid van andere MOFs met vrije metaalsites systematisch na te gaan. Het tweede deel van deze thesis behandelt de adsorptieve eigenschappen van MOFs in de vloeistoffase. Twee structureel gelijkaardige MOFs, MIL-47 en MIL-53, respectievelijk een vanadium- en een aluminiumtereftalaat, worden ingezet voor de adsorptie van aromaten. Hun potentieel voor scheidingen wordt nagegaan met doorbraakexperimenten met behulp van kolommen gevuld met MOF kristallieten. De mechanismen die aan de basis liggen van de waargenomen selectiviteiten worden bestudeerd met verschillende types batchexperimenten, en de adsorbaatmolecules worden gelocaliseerd in de poriën met behulp van Rietveldverfijningen op X-stralenpatronen van verzadigde stalen adsorbens. De scheiding van C8-alkylaromaten, een technologisch uitdagend probleem in de industrie, kan gerealiseerd worden met MIL-47: dit materiaal maakt een onderscheid tussen para-xyleen, meta-xyleen en ethylbenzeen. Met MIL-47 kunnen zuivere isomeren vanuit mengsels van C8-alkylaromaten bekomen worden met gelijkaardige of hogere selectiviteiten in vergelijking met de zeolieten die in de industrie gebruikt worden. De waargenomen selectiviteiten zijn grotendeels het gevolg van de efficiëntie waarmee de aromaten in de poriën gestapeld worden. De capaciteit en selectiviteit van MIL-47 voor adsorptie van aromaten is sterk afhankelijk van de voorbehandeling van het materiaal, gericht op het verwijderen van niet-ingebouwd tereftaalzuur uit de poriën, terwijl een gelijktijdige oxidatie die MIL-47 omzet inniet-poreus V2O5 vermeden moet worden. Wanneer optimaal voorbehandeld MIL-47 gebruikt wordt, wordt telkens het para-isomeer van ethyltolueen, dichlorobenzeen, toluidine en cresol geprefereerd boven het respectievelijke meta-isomeer in puls- en batchexperimenten. Het belang van stapeling in de selectieve adsorptie van deze isomeren wordt besproken. Para- en meta-dichlorobenzeen kunnen van elkaar gescheiden worden in een doorbraakexperiment. MIL-53 werd onderzocht voor selectieve adsorptie en scheiding van xylenen en ethylbenzeen, ethyltoluenen en cymenen. In alle geteste omstandigheden toont MIL-53 de grootste affiniteit voor het ortho-isomeer van elke groep van alkylaromatische componenten. Echte scheidingen van de ortho-isomeren van de andere isomeren kunnen bekomen worden met een kolom gevuld met MIL-53 kristallieten. De positionering van de geadsorbeerde moleculen in de poriën en hun enthalpische interacties met de poriewanden bepalen de selectiviteit. De scheiding van ethyltolueen- en cymeenisomeren gebeurt meer effectief op MIL-53 dan op MIL-47. De hoge selectiviteiten en opnamecapaciteiten van zowel MIL-53 als MIL-47 voor aromaten zijn veelbelovend voor toepassingen van MOFs in scheidingsprocessen.Table of contents Dankwoord i Publications iii Table of contents v Abstract ix Samenvatting xi List of abbreviations xiii Chapter 1: Metal-Organic Frameworks, a novel family of microporous materials 1 1.1 Introduction 3 1.2 Definition and properties of Metal-Organic Frameworks 3 1.3 Synthesis by design 6 1.4 Selected functionalities and their applications 7 1.4.1 Catalytic properties of MOFs 8 1.4.2 Adsorptive properties of MOFs 12 1.5 Thesis objectives and outline 13 Chapter 2: Probing the Lewis Acidity and Catalytic Activity of the Metal-Organic Framework [Cu3(BTC)2] 17 2.1 Introduction 19 2.2 Experimental 20 2.2.1 Instrumentation 20 2.2.2 Synthesis of catalysts 21 2.2.3 Catalytic reactions 23 2.3 Results 24 2.3.1 Characterization 24 2.3.2 Isomerization of α-pinene oxide 28 2.3.3 Cyclization of citronellal 32 2.3.4 Heterogeneity and re-usability of [Cu3(BTC)2] 34 2.3.5 Rearrangement of the ethylene acetal of 2-bromopropiophenone 38 2.3.6 Diels-Alder reactions 39 2.3.7 IR spectroscopy of adsorbed probe molecules 41 2.4 Discussion 43 2.5 Conclusion 44 Chapter 3: Selective Adsorption and Separation of C8 Alkylaromatics and other Disubstituted Aromatics with the Microporous Vanadium(IV) Terephthalate MIL-47 45 3.1 Introduction 47 3.2 Experimental 49 3.2.1 Synthesis of MIL-47 49 3.2.2 Characterization of MIL-47 49 3.2.3 Liquid phase adsorption experiments 50 3.2.4 Gas phase adsorption experiments 51 3.2.5 Crystal structure analysis 51 3.3 Results and discussion 53 3.3.1 Activation of MIL-47 53 3.3.2 Selective adsorption and separation of C8 alkylaromatics 58 3.3.3 Influence of activation conditions on xylene adsorption 64 3.3.4 Adsorption of disubstituted aromatics 65 3.4 Conclusion 68 Chapter 4: Selective Adsorption and Separation of ortho-Substituted Alkylaromatics with the Microporous Aluminium Terephthalate MIL-53 71 4.1 Introduction 73 4.2 Experimental 74 4.2.1 Synthesis of materials 74 4.2.2 Adsorption experiments 75 4.2.3 Crystal structure analysis 75 4.3 Results and discussion 75 4.3.1 Adsorption of alkylaromatics by MIL-53 75 4.3.2 Rietveld refinements 82 4.3.3 Adsorption of alkylaromatics by MIL-47 85 4.4 Conclusion 88 General Conclusions 89 Appendix A: Thermogravimetric measurements on MIL-47 93 Appendix B: Notes on the disorder of xylene and ethylbenzene molecules in the MIL-47 framework 97 Appendix C: Refined XRD-patterns of C8 alkylaromatics in MIL-47 103 Appendix D: Refined XRD-patterns of C8 alkylaromatics in MIL-53 107 References 109status: publishe

Impact of Bio-Based Plastics on Current Recycling of Plastics

Bio-based plastics are increasingly appearing in a range of consumption products, and after use they often end up in technical recycling chains. Bio-based plastics are different from fossil-based ones and could disturb the current recycling of plastics and hence inhibit the closure of plastic cycles, which is undesirable given the current focus on a transition towards a circular economy. In this paper, this risk has been assessed via three elaborated case studies using data and information retrieved through an extended literature search. No overall risks were revealed for bio-based plastics as a group; rather, every bio-based plastic is to be considered as a potential separate source of contamination in current recycling practices. For PLA (polylactic acid), a severe incompatibility with PET (polyethylene terephthalate) recycling is known; hence, future risks are assessed by measuring amounts of PLA ending up in PET waste streams. For PHA (polyhydroxy alkanoate) there is no risk currently, but it will be crucial to monitor future application development. For PEF (polyethylene furanoate), a particular approach for contamination-related issues has been included in the upcoming market introduction. With respect to developing policy, it is important that any introduction of novel plastics is well guided from a system perspective and with a particular eye on incompatibilities with current and upcoming practices in the recycling of plastics

Impact of Bio-Based Plastics on Current Recycling of Plastics

© 2018 by the author. Bio-based plastics are increasingly appearing in a range of consumption products, and after use they often end up in technical recycling chains. Bio-based plastics are different from fossil-based ones and could disturb the current recycling of plastics and hence inhibit the closure of plastic cycles, which is undesirable given the current focus on a transition towards a circular economy. In this paper, this risk has been assessed via three elaborated case studies using data and information retrieved through an extended literature search. No overall risks were revealed for bio-based plastics as a group; rather, every bio-based plastic is to be considered as a potential separate source of contamination in current recycling practices. For PLA (polylactic acid), a severe incompatibility with PET (polyethylene terephthalate) recycling is known; hence, future risks are assessed by measuring amounts of PLA ending up in PET waste streams. For PHA (polyhydroxy alkanoate) there is no risk currently, but it will be crucial to monitor future application development. For PEF (polyethylene furanoate), a particular approach for contamination-related issues has been included in the upcoming market introduction. With respect to developing policy, it is important that any introduction of novel plastics is well guided from a system perspective and with a particular eye on incompatibilities with current and upcoming practices in the recycling of plastics.status: publishe

A Materials Bank for Circular Leuven: How to Monitor ‘Messy’ Circular City Transition Projects

In recent years, cities have revealed themselves as being prominent actors in the circular economy transition. Besides supporting and initiating urban projects catalyzing circularity, cities are looking for monitoring tools that can make their progress towards circularity visible. Adopting Leuven’s pilot project for a building materials bank as a case study, this paper notes the particular challenges and opportunities in the pilot project to assess its progress and impact, in combination with gathering data for overall circular city monitoring purposes. Firstly, the paper names tensions between the “messy” transition process from policy ambitions to implementation and the question of data and monitoring. Secondly, the paper identifies relevant dimensions and scales to evaluate progress and impacts of a building materials bank, drawing from its development process. Thirdly, it proposes guidelines to monitor and evaluate circular city projects from the bottom up, combining quantitative indicators with guiding questions in a developmental evaluation. The analysis serves a critical reflection, distills lessons learned for projects contributing to circular cities and feeds a few concluding policy recommendations. The case study serves as an example that, in order to move beyond the tensions between circularity monitoring and actual circular city project development, monitoring instruments should simultaneously interact with and feed the circularity transition process. Therefore, dedicated data governance driven by enhanced stakeholder interactions should be inscribed in transition process guidance. Bottom-up projects such as a building materials bank provide opportunities to do this

Retrospective and prospective material flow analysis of the post-consumer plastic packaging waste management system in Flanders

The post-consumer plastic packaging waste management in Flanders was analyzed by performing a retrospective material flow analysis, covering an extensive period from 1985 to 2019. In addition, a prospective material flow analysis of 32 improvement scenarios was performed, based on expected changes in the waste management system. Mass recovery rates were calculated based on different interpretations of the calculation rules. Moreover, various cascading levels were identified to differentiate between the quality level of the secondary applications. The mass recovery rate including only recycling evolved from a value of 0% in 1985 to 31% in 2019 and could be increased to 36-62% depending on the improvement scenario selected. However, the different interpretations of the calculation rules led to a variation of up to 20 and 41% on this mass recovery rates for the retrospective and prospective analysis, respectively. The introduction of monostream recycling for additional post-consumer plastic packaging flows, such as low-density polyethylene, did not lead to increasing mass recovery rates, if no differentiation for the cascading levels was made. The Belgian recycling target of 65% for 2023 will be challenging if the strictest calculation method needs to be followed or if the improvements in the Flemish postconsumer plastic packaging waste system do not follow the best-case collection scenarios under the given assumptions. To harmonize the calculation and monitoring of these targets, clear calculation rules need to be accompanied with a harmonized monitoring system over the entire waste management system