Metal-Organic Frameworks in Germany: from Synthesis to Function

Metal-organic frameworks (MOFs) are constructed from a combination of inorganic and organic units to produce materials which display high porosity, among other unique and exciting properties. MOFs have shown promise in many wide-ranging applications, such as catalysis and gas separations. In this review, we highlight MOF research conducted by Germany-based research groups. Specifically, we feature approaches for the synthesis of new MOFs, high-throughput MOF production, advanced characterization methods and examples of advanced functions and properties

SURFACE ENGINEERING OF COLLOIDAL SEMICONDUCTOR NANOCRYSTALS FOR POTENTIAL APPLICATIONS IN DIAGNOSTICS

Ph.DDOCTOR OF PHILOSOPH

Preparation of catalysts from biosorbents supported on zeolites

Tese de doutoramento em Engenharia Química e BiológicaHeavy metal contamination of aquifers by industrial effluents is a known environmental concern for which a recent effort for the development of treatment/remediation technologies has been conducted. Nevertheless, technologies that allow recuperation/reutilization of the metals are still of limited application. This work presents the development of a clean technology allowing treatment and recovery of heavy metals in industrial effluents. The proposed recovered metals will be used as catalysts in liquid-phase oxidation reactions. The proposed system consists in bridging the biosorption capacity of the Arthrobacter viscosus bacterium with the intrinsic ion-exchange capacity of synthetic zeolites. This system was tested in the treatment of Cr(VI) solutions, in batch conditions (either in single step or sequencing reactor operation). The system showed capacity for the treatment of Cr(VI) solutions. Although zeolites have natural limitation to exchanging Cr(VI) species, as they are anionic in solution, the bacterium is able to reduce Cr(VI) to Cr(III) and the last is cationic in solution and therefore has access to the zeolites. Several operational parameters were evaluated in order to increase the performance of this system in the treatment of Cr(VI) solutions up to 100 mgCr/g. The pH in each reactor was allowed to vary freely in early studies. It was observed that the chemical composition of the zeolitic support had influence on the efficiency of the bioreduction of Cr(VI) to Cr(III). H+- containing zeolites allowed higher reduction than the Na+-containing counterparts. Despite this fact, subsequent studies demonstrated that this contribution was of minor effect when compared to the optimization of two parameters: biomass concentration and solution pH. The ensuing studies were performed with a biomass concentration of 5 g/L and controlled pH (4.0). Four zeolites were tested, HY, NaY, HMOR and NaMOR. In both single-step or sequencing reactor operation, Y zeolites demonstrated higher contribution to Cr(VI) reduction and overall chromium removal. In single-step operation, it was observed that the reduction of Cr(VI) follows a typical biosorption kinetics, being very fast during the first 24 hours, decreasing drastically thereafter. The highest uptake was achieved with the NaY support (11.7 mgCr/gzeolite), after 27 days. This support was also tested in a long-term assay, where complete reduction of Cr(VI) was observed after 98 days. The operation in sequencing batch reactor allowed reducing the time needed for complete Cr(VI) removal, requiring two four-day cycles with HY and NaY zeolites and three four-day cycles with HMOR and NaMOR zeolites. Maximum chromium removal was achieved with the HY support (98.2 %). The recovery of the Cr-containing supports as catalysts was achieved. Cr-laden zeolites required that immobilization of the metal centers was performed prior to the application in liquid-phase reactions, in order to avoid leaching of chromium. The Cr-zeolites underwent immobilization of the metals through the flexible ligand method, using ligands with different nitrogen functional groups (pyridazine, pyridylazo and diphenyltriazene). All supports and catalysts were extensively characterized, confirming the successful immobilization of Cr(III) complexes in Y zeolites. It was observed that CrHY-based catalysts presented mostly Cr(III) in their structure, whereas CrNaY-based catalysts presented both Cr(VI) and Cr(III). This was found to be related to the different dynamics of both supports in the Cr(VI) biotreatment studies. The catalytic activity of the catalysts was evaluated in two oxidation reactions, for cyclohexanol and cyclohexanone. The oxidation of cyclohexanol allowed a better understanding of the contribution of the different chromium species present. The highest conversion for this reaction was obtained with CrNaY-based catalysts (63.5 %). The presence of chromium in the reaction medium was confirmed, being of lesser extent when immobilized catalysts were employed. For the oxidation of cyclohexene, CrHY-based catalysts achieved the highest conversion of 73 %. It was found that the contribution of parent HY zeolite to the overall conversion was greater than of parent NaY zeolite, thus endowing CrHY catalysts with bi-functionality. The immobilized CrHY catalyst did not present significant decrease in activity after immobilization of chromium complexes, when compared to the parent support. For both reactions, it was possible to test the reuse of a CrNaY support and respective immobilized catalyst, confirming that the loss in activity with recycling was less pronounced when immobilized catalysts were used.A contaminação de aquíferos por efluentes industriais contendo metais pesados é um problema ambiental para o qual houve um esforço recente no sentido de desenvolver tecnologias para minimizar os efeitos nos seres vivos. Apesar desses esforços, tecnologias que permitam recuperação/reutilização dos metais pesados são limitadas ou economicamente inviáveis. Neste âmbito, este trabalho propõe uma tecnologia limpa para tratamento e recuperação de efluentes contaminados com metais pesados que permita a reutilização dos metais na forma de catalisadores para reacções de oxidação em fase líquida. O sistema proposto consiste na combinação das propriedades de biossorção de uma bactéria, Arthrobacter viscosus, com a capacidade intrínseca de permuta iónica de zeólitos sintéticos do tipo faujasite e mordenite. Este sistema foi testado no tratamento de soluções contendo crómio hexavalente, Cr(VI), em sistema fechado (mono-etapa ou em modo sequencial). O sistema provou ser eficaz no tratamento das soluções de Cr(VI). Apesar dos zeólitos terem uma limitação natural à permuta de crómio hexavalente (que forma espécies aniónicas em ambiente aquoso), a bactéria é capaz de reduzir Cr(VI) a Cr(III), que existe em forma catiónica e é passível de permuta iónica no zeólito. Vários parâmetros operacionais foram testados para melhorar o desempenho do sistema no tratamento de soluções de Cr(VI) com concentração máxima de 100 mgCr/L. Após estudos iniciais com pH livre, observou-se que a composição do suporte zeolítico interfere na eficácia da redução do Cr(VI) a Cr(III). Os zeólitos contendo iões H+ provaram ser mais eficazes que os zeólitos contendo iões Na+. Contudo, estudos posteriores demonstraram que a contribuição do suporte na redução do Cr(VI) é de menor efeito quando comparado com os resultados obtidos optimizando dois parâmetros: concentração de biomassa e pH da solução. Os estudos posteriores foram efectuados com uma concentração de biomassa de 5 g/L, a um pH controlado (4.0). Foram testados 4 zeólitos, HY, NaY, HMOR e NaMOR. Quer em sistema fechado de mono-etapa ou sequencial, os zeólitos Y demonstraram maior contribuição para a redução e remoção do crómio presente nas soluções. Em sistema monoetapa, observou-se que a redução do Cr(VI) está de acordo com uma cinética típica de biossorção, sendo um processo rápido nas primeiras 24 horas de ensaio, diminuindo drasticamente nos intervalos de tempo subsequentes. O suporte que permitiu maior uptake foi o NaY (11.7 mgCr/gzeólito), ao fim de 27 dias. Este suporte foi testado num ensaio de longa duração, 98 dias, em que se observou a redução completa de uma solução de 100 mgCr/L. A operação em sistema sequencial permitiu reduzir o tempo necessário para a redução completa do Cr(VI), sendo necessários 2 ciclos de 4 dias para os suportes HY e NaY e 3 ciclos de 4 dias para os suportes HMOR e NaMOR. Neste modo, a remoção máxima de crómio foi alcançada com o suporte HY (98.2 %). A recuperação dos suportes contendo crómio na forma de catalisadores foi conseguida. Os zeólitos com crómio necessitaram um tratamento prévio para imobilizar os centros metálicos na sua estrutura, de forma a evitar a lixiviação dos mesmos para o meio reaccional. Para o efeito, recorreu-se ao método do ligando flexível, usando ligandos contendo azoto em diferentes grupos estruturais (piridazina, piridilazo e difeniltriazeno). Todos os suportes foram extensivamente caracterizados, confirmando-se a imobilização de complexos de Cr(III) na estrutura de zeólitos Y. Observou-se que os suportes CrHY apresentam maioritariamente Cr(III) na sua estrutura e os suportes CrNaY apresentam Cr(VI) e Cr(III). Este facto foi relacionado com as dinâmicas diferentes observadas nos estudos de tratamento de soluções de Cr(VI). A avaliação da actividade dos catalisadores foi efectuada em duas reacções de oxidação, do ciclohexeno e do ciclohexanol. A reacção do ciclohexanol permitiu um melhor entendimento das contribuições das diferentes espécies de crómio presentes. Nesta reacção, os catalisadores CrNaY obtiveram as conversões mais elevadas (63.5 %). Foi confirmada a presença de crómio no meio reaccional, sendo em menor quantidade no caso dos catalisadores que sofreram o processo de imobilização do metal. Na oxidação do ciclohexeno, os catalisadores CrHY demonstraram maior actividade, devida à maior contribuição do zeólito HY na reacção, em relação ao NaY. Neste aspecto, os catalisadores CrHY demonstraram bifuncionalidade, alcançando uma conversão máxima de 73 %. Os suportes CrHY e respectivos catalisadores não apresentaram diminuição de actividade após imobilização do crómio. Para as duas reacções, foi possível estudar a comparação da reutilização de suportes CrNaY e dos respectivos catalisadores imobilizados, sendo observada uma menor perda de actividade em cada ciclo no caso dos catalisadores imobilizados

Immobilization of Enzymes on Hierarchically-Structured Supports

In the last decades, the energy consumption of the world has been dramatically enlarged, owing to increased globalization and the economic growth. Thus, new renewable energy sources have been developed to overcome this drawback. In recent years, biomass, which is one of the most widespread renewable energy sources, promises to satisfy this demand. Biomass is also utilized as a sustainable resource to be situated for some valuable chemicals as well as biofuels and biopolymer intermediates. Conversion of biomass can be accomplished by catalytic processes in which enzymes play a key role as biocatalysts. Contrary to the side effects of many physical and chemical processes in industry, biocatalysis has been preferred due to their inhibition of the environmental pollution. Contrary to chemical catalysts, enzymes are used under mild conditions due to their proverbial sensibility and limited operational stability. These features of enzymes cause some challenges in recovery and reusability for a given industrial application. In order to enhance stability of enzymes-based catalysts, immobilization techniques were improved. Besides, many scientists investigate with a great interest the most effective way to obtain maximized exposure of enzyme’s active site in the biocatalytic reaction mixture, with an obvious impact in the catalyst activity. A suitable strategy for the above described issue is usually to be benefit from a porous support, which should provide suitable binding sites for enzymes in active conformation, and/or allow encapsulation of enzymes, whilst minimizing enzyme leakage and deactivation. Additionally, the characteristics of a carrier utilized in immobilization of enzyme have to be well-considered including its permeability, surface area, hydrophilic character, insolubility, mechanical and thermal stability. While keeping in mind of the above-described properties, it is not a surprise that inorganic porous materials are commonly preferred due to their cage-like configurations, which allow the constructions of suitable microenvironments for enzymes. Inorganic porous materials present very interesting features, such as tunable pore size and shape, high specific surface area, high chemical and structural stability, and a variety of chemical functionalities, which can be used as anchoring sites for hosted enzymes. They also possess many advantages, such as increasing enzyme stability, protecting enzymes from harsh reaction conditions, having ability of tailored-cages construction for different enzyme sizes, etc. In this thesis, several different inorganic porous supports were used for enzyme immobilization. These are gradient macroporous stainless steel discs (GMSDs), gradient nanoporous ceramic discs (GNCDs), microporous zeolites, metal organic frameworks (MOFs), and silica-based nanoparticles (SiO2). In addition to that, several chemical catalysts were employed in biomass conversion. Hierarchical nanosheet zeolites, zeolitic imidazolate frameworks (ZIFs) as well as zinc oxide (ZnO) were tested in isomerization of monosaccharides. From the point of biomass type, starch became prominent in this thesis since it is a kind of primary biomass which appears abundantly in nature. This polysaccharide is constructed from glucose units linked with each other via glycosidic bonds and highly exploited in numerous applications in industry. There are several enzymes available for converting starch molecules. Here, we used α-amylase (and thermostable α-amylase) and ß-amylase to hydrolyze the starch to glucose. Additionally, α-glucosidase to hydrolyze maltose to glucose, invertase to hydrolyze sucrose to glucose and fructose and glucose oxidase to oxidase β-D-glucose to D-glucono-δ-lactone were employed. Alongside of the carbohydrate enzymes, lipases are also commonly used in many industrial applications. In this thesis, lipase from Thermomyces lanuginosus to perform transesterification of vinyl propionate (VP) with 1butanol as well as lipase from Aspergillus niger to hydrolase p-nitrophenyl palmitate to p-nitrophenol were tested. The specificity of an enzyme, the versatile activation of a chemical catalyst and the utility of inorganic porous materials in immobilization of enzymes allow several different designs for process engineering. Consequently, combining of biocatalysts and inorganic porous materials in order to achieve much more efficient reaction mechanisms is mainly focused on in this thesis

Sol-gel based materials for biomedical applications

Sol-gel chemistry offers a flexible approach to obtaining a diverse range of materials. It allows differing chemistries to be achieved as well as offering the ability to produce a wide range of nano-/micro-structures. The paper commences with a generalized description of the various sol-gel methods available and how these chemistries control the bulk properties of the end products. Following this, a more detailed description of the biomedical areas where sol-gel materials have been explored and found to hold significant potential. One of the interesting fields that has been developed recently relates to hybrid materials that utilize sol-gel chemistry to achieve unusual composite properties. Another intriguing feature of sol-gels is the unusual morphologies that are achievable at the micro- and nano-scale. Subsequently the ability to control pore chemistry at a number of different length scales and geometries has proven to be a fruitful area of exploitation, that provides excellent bioactivity and attracts cellular responses as well as enables the entrapment of biologically active molecules and their controllable release for therapeutic action. The approaches of fine-tuning surface chemistry and the combination with other nanomaterials have also enabled targeting of specific cell and tissue types for drug delivery with imaging capacity

Abatement of phosphorus- and lead-induced environmental risks by means of apatite ore mine tailings

Mining of phosphorus (P) and lead (Pb) ores increases their amounts in biogeochemical cycles and, consequently, their environmental risks. Phosphorus is an important nutrient, but P loading from sewage waters and agricultural activities to watercourses may result in eutrophication, a process eventually detrimental to aquatic ecosystems. Lead, on the other hand, poses a direct risk of intoxication to all living organisms. In addition to technical applications, Pb is used in pellets and shots on shooting ranges, which accounts for a large source of Pb loading to the environment. Prevention and abatement of detrimental impacts of P and Pb require large-scale, cost-effective techniques that do not compromise the environment. This thesis was undertaken to investigate the potential of tailings from apatite ore beneficiation at the Siilinjärvi phosphate mine, Finland, in the dephosphorization of sewage and in the remediation of metal-contaminated areas. The material is a mixture of minerals, mainly phlogopite [KMg3(Si3Al)O10(OH)2] and calcite (CaCO3), accompanied by apatite [Ca5(PO4)3F] residues. Based on the versatile chemical properties, this geomaterial was hypothesized to act as a sorbent for P and Pb, rendering the tailings a potential agent for environmental remediation. A part of the original tailings material was artificially weathered by treating with a strong acid to create reaction-active aluminium (Al) and iron (Fe) (hydr)oxide sites. Some of the acidified material was further subjected to partial neutralization by treating with a strong base to precipitate any metals dissolved from the mineral structure during the acidification. Furthermore, all of the tailings materials were sieved into two particle-size fractions somewhat differing in their mineralogical composition and investigated as separate amendments. The ability of the tailings to retain P and Pb from aqueous solutions as well as the tailings-induced changes in the Pb retention capacity of a mineral soil were studied by means of an isotherm technique. A sequential fractionation procedure was undertaken to investigate (a) the distribution of inherent and added P between various chemical pools in the tailings and (b) the tailings-induced changes in the distribution of Pb between various chemical pools in a mineral soil artificially contaminated with Pb as well as in an organic shooting range soil contaminated with pellet-derived Pb. Because the toxicity of dissolved Pb depends on its chemical speciation, the tailings-induces changes in the chemical speciation of water-extractable Pb in contaminated shooting range soil was tested separately by means of a cation exchange resin. The tailings retained both P and Pb efficiently. The removal of soluble P was primarily due to specific sorption by Al and Fe (hydr)oxides and possibly to retention to calcite. Lead sorption by the untreated tailings was a combination of various sorption mechanisms taking place simultaneously, primarily through precipitation and surface complexation. All tailings materials increased the Pb sorption capacity of a mineral soil and transferred Pb from the NH4NO3-extractable pool to the more strongly bound forms. In a contaminated shooting range soil, the pellets were found to undergo continuous weathering processes that released Pb into the soil. Amending the soil with the untreated tailings (a) reduced the solubility of the pellet-derived Pb through the formation of sparingly soluble fluorpyromorphite and cerussite, (b) reduced the bioavailability of Pb by transferring it from the water-soluble and NH4NO3-extractable pools into the NaOH-extractable one and (c) transferred the most toxic cationic Pb species to the less toxic non-cationic form. The results suggest that the tailings may serve as an agent for dephosphorization of sewage and for Pb immobilization in polluted soil. The sorption properties of the material may be further optimized by chemical and physical pre-treatments. At present, the tailings material represents an uneconomic fraction of the ore deposit, but its components may render it a natural, environmentally sound and cost-effective remediation agent.Kaivostoiminta nopeuttaa ratkaisevasti kallioperän alkuaineiden päätymistä luonnonkiertoon. Kallioperän mineraalivarannoista louhitaan kasvinravinteita lannoiteteollisuuden käyttöön samoin kuin eliöille haitallisia metalleja ja metalloideja teollisiin tarkoituksiin. Fosfori on välttämätön kasvinravinne, mutta sen lisääntyneet päästöt vesiluontoon voivat aiheuttaa haitallista rehevöitymistä. Suurimpia vesistöjen fosforikuormittajia ovat maatalouden valumavedet sekä viemäriverkoston ulkopuoliset jätevedet. Lyijy puolestaan on kaikille eliöille myrkyllinen raskasmetalli. Sen lukuisista käyttötarkoituksista tunnetuimpia ovat akut ja haulit. Suomessa ampumatoiminta on aiheuttanut merkittävää ympäristön pilaantumista. Fosforista ja lyijystä aiheutuvien ympäristöhaittojen torjumiseksi tarvitaan ekologisesti kestäviä ja edullisia ratkaisuja. Tässä väitöskirjassa tutkittiin, voitaisiinko Siilinjärven fosforikaivoksella apatiittimalmin rikastamisen sivutuotteena muodostuvaa kiviainesta eli rikastushiekkaa käyttää fosforin ja lyijyn sitojana. Rikastushiekka koostuu pääasiassa flogopiitista, kalsiitista sekä rikastusprosessissa hyödyntämättä jäävästä apatiitista. Monipuolisten mineralogisten ominaisuuksiensa ansiosta rikastushiekan oletettiin pystyvän pidättämään fosforia ja lyijyä erilaisin mekanismein ja näin poistamaan jätevesistä fosforia sekä immobilisoimaan lyijyä ampumaratamaista. Kokeissa tutkittiin käsittelemättömän rikastushiekan lisäksi ainesta, joka oli esikäsitelty väkevällä hapolla mineraaliaineksen rapauttamiseksi ja reaktioaktiivisen raudan ja alumiinin oksidien muodostamiseksi. Osa hapotetusta rikastushiekasta käsiteltiin edelleen väkevällä emäksellä mineraalirakenteista liuenneiden metallien saostamiseksi. Sekä käsittelemätön että kemiallisesti esikäsitelty aines jaettiin seulomalla kahteen mineralogialtaan toisistaan jonkin verran poikkeavaan hiukkaskokoluokkaan, joita tutkittiin erillisinä materiaaleina. Systemaattisissa kokeissa selvitettiin, miten eri rikastushiekkamateriaalit pystyvät pidättämään fosforia ja lyijyä vesiliuoksista samoin kuin pidättymisen todennäköisiä mekanismeja sekä materiaalien vaikutusta mineraalimaan lyijynpidätyskykyyn. Uuttotesteissä tutkittiin, miten rikastushiekan luontainen fosfori ja pidätyskokeissa sitoutunut fosfori jakautui liukoisuudeltaan erilaisiin luokkiin, joiden katsottiin edustavan erilaisia pidätyspintoja. Lyijyllä keinotekoisesti saastutetulla mineraalimaalla ja ampumatoiminnan kuormittamalla orgaanisella maalla tehdyissä uuttotesteissä selvitettiin, miten lyijy jakautui erityyppisten pidättävien hiukkaspintojen välillä. Koska liukoisen lyijyn myrkyllisyys eliöille riippuu sen kemiallisesta esiintymismuodosta, tutkittiin työssä myös rikastushiekan vaikutusta vesiuuttoisen lyijyn spesiaatioon. Tutkimustulokset osoittivat rikastushiekan pidättävän tehokkaasti sekä fosforia että lyijyä. Liukoinen fosfori pidättyi pääasiassa rikastushiekan alumiini- ja rauta(hydr)oksidien pinnalle sekä todennäköisesti jossain määrin myös kalsiittiin. Happokäsittely lisäsi materiaalin fosforinpidätyskykyä oleellisesti. Käsittelemätön rikastushiekka pidätti myös liukoista lyijyä muodostamalla sen kanssa heikkoliukoisia saostumia sekä pintakomplekseja. Sekä käsittelemätön että happokäsitelty rikastushiekka lisäsivät mineraalimaan lyijynpidätyskykyä ja siirsivät biosaatavaa lyijyä tiukemmin pidättyneeseen muotoon. Lyijyllä saastuneella ampumaratamaalla tehdyissä kokeissa huomattiin, että hauleista vapautuu jatkuvasti lyijyä maaperään. Käsittelemättömän rikastushiekan lisääminen maahan kuitenkin vähensi hauleista peräisin olevan lyijyn liukoisuutta muodostamalla sen kanssa heikkoliukoisia fosfaatti- ja karbonaattiyhdisteitä. Rikastushiekka myös vähensi lyijyn biosaatavuutta ja siten ekotoksisuutta maassa. Tulosten perusteella Siilinjärven rikastushiekka voi soveltua jätevesien fosforinpoistoon ja lyijyn immobilisointiin saastuneilla maa-alueilla. Materiaalin pidätysominaisuuksia voidaan optimoida erilaisin kemiallisin ja fysikaalisin esikäsittelyin. Tulevaisuudessa tämä nykyisellään jätteenä läjitettävä geomateriaali saattaa tarjota luonnonmukaisen, ympäristöystävällisen ja kustannustehokkaan keinon erilaisiin ympäristön kunnostustarpeisiin

Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 1

Papers from the technical sessions of the Technology 2001 Conference and Exposition are presented. The technical sessions featured discussions of advanced manufacturing, artificial intelligence, biotechnology, computer graphics and simulation, communications, data and information management, electronics, electro-optics, environmental technology, life sciences, materials science, medical advances, robotics, software engineering, and test and measurement