Synthesis and engineering of metal-organic frameworks for liquid phase applications

Metal-organic frameworks (MOFs) are a class of highly versatile porous materials expressing previously unobserved high surface areas and tuneable both internal and external chemical environments. However, the current shortfall of these structures is insufficient data on their chemical stability as well as the lack of a standardised stability testing approach across literature. Thus, the aims of this work are two develop a comparable way of probing the water stability of MOFs as well as to test their applicability for micro-pollutant capture purposes. UiO-66 MOF showed poor stability in basic environment followed by moderate instability in neutral conditions. On the other hand, the inclusion of functional groups on UiO-66 confer a metal cluster shielding effect which can effectively prevent the diffusion of attacking chemical species into the MOF. Even in large pore size MOFs, the pore collapse inducing capillary effects during direct activation from water can be navigated by inclusion of hydrophobic functionalities. The poor stability of powdered ZIF-8 in acidic media and even in neutral conditions is attested. More importantly, the kinetic stability of ZIF-8 is dramatically improved by shaping into a pure phase monolithic MOF using a sol-gel synthesis process. Whereas the stability of monolithic UiO-66 and MOF-808 still needs improvement, it was found that monolithic MOF- 808 is successfully activated from water after stability testing with almost complete retention of original porosity, its powdered analogue suffered complete amorphisation under the same conditions. The current dissertation also presents a in-situ growth procedure of ZIF-8 on open frontal area honeycomb ceramic cordierite substrate. By tailoring the surface chemistry of the substrate, especially with ZnO, it was found that the growth of ZIF-8 was significantly enhanced, to achieve a uniform and complete surface coverage. ZIF-8 and UiO-66 MOFs were investigated for adsorption of endocrine disruptor micro-pollutant, bisphenol B (BPB). Whereas both MOFs promise very rapid uptake within less than 30 minutes of contact, their respective structural intricacies and stability limitations affect their removal capabilities. Most importantly, the monolithic ZIF-8 configuration yielded superior performance in both flow and batch mode conditions.EPSR

Brainstem Auditory Evoked Potentials in Raccoon Dogs

Raccoon dogs (Nyctereutes procynoides) are canids indigenous to Eastern Asia being one of the most invasive non-native animals in Europe and potential vectors for several hazardous parasitic and viral diseases. To present, there is a lack of studies regarding objective techniques used to appreciate the integrity and functionality of the nervous system in this species. Brainstem auditory evoked potentials (BAER) is a cost-e ective, quick and noninvasive technique to assess the functionality of nervous system. The aim of the study is to provide reference values and evaluates the reliability of BAER recording with needle electrodes in clinically healthy raccoon dogs. Nine individuals were investigated for BAER under xylazine and ketamine general anesthesia. Four waves (I, II, III and V) were identified and evaluated for latencies, morphologically similarity to those previously reported for other species (dogs, horses, cats, and ferret). Our data can be used in further studies to asses objectively the auditory system function in raccoon dogs

Core-Shell Gold Nanorod@Zirconium-Based Metal-Organic Framework Composites as in Situ Size-Selective Raman Probes.

Nanoparticle encapsulation inside zirconium-based metal-organic frameworks (NP@MOF) is hard to control, and the resulting materials often have nonuniform morphologies with NPs on the external surface of MOFs and NP aggregates inside the MOFs. In this work, we report the controlled encapsulation of gold nanorods (AuNRs) by a scu-topology Zr-MOF, via a room-temperature MOF assembly. This is achieved by functionalizing the AuNRs with poly(ethylene glycol) surface ligands, allowing them to retain colloidal stability in the precursor solution and to seed the MOF growth. Using this approach, we achieve core-shell yields exceeding 99%, tuning the MOF particle size via the solution concentration of AuNRs. The functionality of AuNR@MOFs is demonstrated by using the AuNRs as embedded probes for selective surface-enhanced Raman spectroscopy (SERS). The AuNR@MOFs are able to both take-up or block molecules from the pores, thereby facilitating highly selective sensing at the AuNR ends. This proof-of-principle study serves to present both the outstanding level of control in the synthesis and the high potential for AuNR@Zr-MOF composites for SERS

Brainstem Auditory Evoked Potentials in Raccoon Dogs (Nyctereutes procynoides)

Raccoon dogs (Nyctereutes procynoides) are canids indigenous to Eastern Asia being one of the most invasive non-native animals in Europe and potential vectors for several hazardous parasitic and viral diseases. To present, there is a lack of studies regarding objective techniques used to appreciate the integrity and functionality of the nervous system in this species. Brainstem auditory evoked potentials (BAER) is a cost-effective, quick and noninvasive technique to assess the functionality of nervous system. The aim of the study is to provide reference values and evaluates the reliability of BAER recording with needle electrodes in clinically healthy raccoon dogs. Nine individuals were investigated for BAER under xylazine and ketamine general anesthesia. Four waves (I, II, III and V) were identified and evaluated for latencies, morphologically similarity to those previously reported for other species (dogs, horses, cats, and ferret). Our data can be used in further studies to asses objectively the auditory system function in raccoon dogs

Engineering New Defective Phases of UiO Family Metal-Organic Frameworks with Water

As defects significantly affect the properties of metal-organic frameworks (MOFs)–from changing their mechanical properties to enhancing their catalytic ability–obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both UiO-67(Hf)and UiO-66(Hf) (F4BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered hcp UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by thisinvestigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes

Engineering New Defective Phases of UiO Family Metal-Organic Frameworks with Water

As defects significantly affect the properties of metal-organic frameworks (MOFs)–from changing their mechanical properties to enhancing their catalytic ability–obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both UiO-67(Hf) and UiO-66(Hf) (F4BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered hcp UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by this investigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes

Engineering New Defective Phases of UiO Family Metal-Organic Frameworks with Water

As defects significantly affect the properties of metal-organic frameworks (MOFs)–from changing their mechanical properties to enhancing their catalytic ability–obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both UiO-67(Hf) and UiO-66(Hf) (F4BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered hcp UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by this investigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes