Stabilization of Scandium Terephthalate MOFs against Reversible Amorphization and Structural Phase Transition by Guest Uptake at Extreme Pressure

Previous high-pressure experiments have shown that pressure-transmitting fluids composed of small molecules can be forced inside the pores of metal organic framework materials, where they can cause phase transitions and amorphization and can even induce porosity in conventionally nonporous materials. Here we report a combined high-pressure diffraction and computational study of the structural response to methanol uptake at high pressure on a scandium terephthalate MOF (Sc2BDC3, BDC = 1,4-benzenedicarboxylate) and its nitro-functionalized derivative (Sc2(NO2–BDC)3) and compare it to direct compression behavior in a nonpenetrative hydrostatic fluid, Fluorinert-77. In Fluorinert-77, Sc2BDC3 displays amorphization above 0.1 GPa, reversible upon pressure release, whereas Sc2(NO2–BDC)3 undergoes a phase transition (C2/c to Fdd2) to a denser but topologically identical polymorph. In the presence of methanol, the reversible amorphization of Sc2BDC3 and the displacive phase transition of the nitro-form are completely inhibited (at least up to 3 GPa). Upon uptake of methanol on Sc2BDC3, the methanol molecules are found by diffraction to occupy two sites, with preferential relative filling of one site compared to the other: grand canonical Monte Carlo simulations support these experimental observations, and molecular dynamics simulations reveal the likely orientations of the methanol molecules, which are controlled at least in part by H-bonding interactions between guests. As well as revealing the atomistic origin of the stabilization of these MOFs against nonpenetrative hydrostatic fluids at high pressure, this study demonstrates a novel high-pressure approach to study adsorption within a porous framework as a function of increasing guest content, and so to determine the most energetically favorable adsorption sites

Development of a semi-automated ZLC system for rapid screening of adsorbents for carbon capture

In this dissertation a novel ZLC setup has been developed as part of a DOE-funded grant in collaboration with UOP, to provide rapid screening of novel adsorbent materials for carbon capture (CC). The key features of the new apparatus that was developed are: the use of 5-15 mg of sample and a dual detector system – a thermal conductivity detector (TCD) for single component measurements and a mass spectrometer for studying the influence of water and other impurities. Improvements over previous ZLC apparatuses include: 1. Extension to lower flowrates, i.e. < 3 cc/min, thereby reducing consumption of gases and allowing to run the system under equilibrium control conditions; 2. A new gas dosing system that allows the use of vapours without a chilled bath and bubbler system; 3. A new switching valve system, which prevents leakages; 4. Automated series of experiments, which are implemented using Labview. The new ZLC technique was first applied to provide rapid screening capacity ranking of more than 15 MOF materials from the open literature and three typical zeolites for carbon capture. At the point of interest for flue gas application (38°C, 0.1 bar CO2 partial pressure), Mg/DOBDC was found to outperform significantly all other MOFs and benchmark zeolites at the point of interest in low pressure physisorption of CO2. The ZLC was also used to investigate steaming on Ni/DOBDC as well as see the effect of forming powders into pellets. The new ZLC system also enables one to measure micropore and macropore diffusivity. Experiments were carried out on both powders and pellets of typical MOFs and zeolites. For Co/DOBDC crystals, since the system is close to equilibrium control even at the highest flow rate, a low limit of diffusivity can be estimated. For all the formed samples of Ni/DOBDC and 13X pellets, the results indicate that mass transfer is controlled by macropore diffusion. The ZLC technique can also estimate realistic void fraction and tortuosity values for the pellets. The new ZLC technique was applied to study the stability on the MOF M/DOBDC series. The preliminary water tests showed that all M/DOBDC samples are highly hydrophilic. Therefore in a process design using these MOFs, we conclude that there is a needs to use a guard bed layer to adsorb water or use a gas drying unit before the CO2 capture section of the plant. The ZLC system appears to be extremely useful to accelerate the deactivation of samples due to SOX and NOX impurities. The key advantages are based on the fact that the treatment can be repeated in situ, in a relatively simple way using a very small sample. The results show that in the presence of impurities and water the candidate MOFs undergo significant deactivation. The Ni based material shows the best resistance to degradation. This result indicates further that there would be a need for a drying unit prior to the carbon capture adsorption process.EThOS - Electronic Theses Online ServiceU.S. Department of Energy and the National Energy Technology Laboratory led by UOP (Award No. DEFC26- 07NT43092)GBUnited Kingdo

Understanding the adsorption process in ZIF-8 using high pressure crystallography and computational modelling

Supporting data for our publication "Understanding the adsorption process in ZIF-8 using high pressure crystallography and computational modelling' to be published in Nature Comm.Moggach, Stephen; Hobday, Claire; Morrison, Carole; Duren, Tina. (2018). Understanding the adsorption process in ZIF-8 using high pressure crystallography and computational modelling, [dataset]. University of Edinburgh. School of Chemistry. http://dx.doi.org/10.7488/ds/2324

STA-27, a porous Lewis acidic scandium MOF with an unexpected topology type prepared with 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine

A porous scandium MOF denoted STA-27 (St Andrews Porous Material-27) has been synthesised solvothermally using the 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine anion (TCPP4-) as the tetratopic carboxylate linker. STA-27 possesses a unique scandium-based 1D rod secondary building unit (SBU) comprising corner-sharing scandium Sc2O11 dimers connected via carboxylate groups from the linker. After activation under mild conditions STA-27 is an active Lewis acidic catalyst, while heating at elevated temperatures results in rupturing of the Sc-O-Sc linkages and a phase transition to a different topological type. Under similar synthesis conditions the smaller Al3+ and Ga3+ cations give isostructural MOFs with a different, previously reported, topology type based on chains of corner-sharing MO4(OH)2 octahedra: the Al-form possesses attractive properties for CO2 adsorption

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially