How reproducible are surface areas calculated from the BET equation?

Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro- and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calculate the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called "BET surface identification" (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible

Developing Commercially Scalable Iron and Titanium Metal-Organic Frameworks for Gas Storage and Water Purification

Since their discovery in the late 1990s, Metal-Organic Frameworks (MOFs) have turned into one of the fastest growing classes of materials studied in the chemical literature. MOFs have shown promise in applications such as gas storage, chemical separations, chemical sensing, catalysis, and even drug delivery. Their wide range of potential applications can be attributed to their ultra-high surface area, high crystallinity and tunable physical and chemical properties. However, the potential applications of MOFs have been slow to develop into viable and sustainable products at the commercial or industrial level. Chapter I of this dissertation discusses the background of Metal-Organic Frameworks (MOFs), the current limitations of MOFs that prevent wide spread commercial production such as stability, processing cost, and synthesis cost as well as how the research performed aimed to address these challenges. In Chapter II details a method that was developed in order to synthesize a Hierarchally Porous (HP) variant of a commercially available MOF named PCN-250(Fe3O). The method developed utilizes the addition of fatty acids during MOF synthesis in order to induce and engineer hierarchal porosity within PCN-250(Fe3O). The resulting Hierarchally Porous MOFs (HP-MOF) exhibited completely different mesoporosity in size, volume, and position. Furthermore, the PCN-250(C9-1.4M) material obtained adsorbs/removes 100% of Methylene Blue, a common organic dye, from aqueous solution, as compared to the microporous variant of PCN-250(Fe3O), which only removes 31% Chapter III builds on the use of PCN-250(Fe3O) as a material for removing organic dyes from water, but utilizes PCN-250(Fe3O) as a catalyst, not just an adsorbent. PCN-250 was reported to be a successful and recyclable Fenton and photo-Fenton catalyst that degrades 100% of Methylene Blue. Overall, 4 different variants of PCN-250 were synthesized and named PCN-250(Fe3O), PCN-250(Fe2Ni), PCN-250(Fe2Co) and PCN-250(Fe2Mn). The catalytic degradation efficiency for both Fenton and photo-Fenton reactions was improved by the isomorphic substitution of Mn and Co for Fe, but inhibited by the incorporation of Ni. Chapter IV details the development of a photo-catalytic system for the degradation of Per/Poly-Fluorinated Alkyl Substances (PFASs) using a commercially scalable Ti-Based MOF. With the developed photo-catalytic system, the concentration of Perfluorooctanoic acid (PFOA) can be reduced by 49% and with a 21.1% fluoride mineralization efficiency in 24 hours. Overall, this work has shown the ability to successfully design Metal-Organic Frameworks based photo-catalytic platforms for chemically reducing (degrading) Per- and polyfluoroalkyl substances (PFAS) in water and is to the best of our knowledge the first successful example of using MOFs for PFAS degradation. Chapter V, details the development of a novel MOF processing method that maximizes the surface area while minimizing cost. The method is a suspension-based processing 3 step method that maximizes the porosity of MOFs by more effectively solubilizing unreacted starting materials and more importantly, removing area of low crystallinity from the surface of MOF particles. In the last chapter, Chapter VI, a summary of the current work is given along with my thoughts and outlooks on future of MOFs

Suspension Processing of Microporous Metal-Organic Frameworks: A Scalable Route to High-Quality Adsorbents

Summary: Metal-Organic Frameworks (MOFs) have been intensively studied for applications such as gas storage, gas separation, catalysis, drug delivery, and more. Typically, the development of MOFs involves a post-synthetic solvent exchange process, which usually requires a significant investment of time, energy, labor, and resources. Herein, we propose a novel post-synthetic processing methodology for commercial and laboratory-scale MOFs called “Suspension Processing.” Suspension processing is a non-destructive, agitation-based technique that provides efficient solvent exchange, pore cleaning, and surface defect removal in MOFs. Suspension processing has shown the capability to significantly improve the surface area and gas uptake properties of microporous MOFs, including PCN-250, UiO-66, and HKUST-1. Suspension processing displays improved time, energy, and labor efficiency, as well as considerably enhanced product quality. These findings confirm suspension processing as a straightforward methodology with applicability as a universal technique for the production of high-quality microporous materials. : Organometallic Chemistry; Materials Science; Porous Material Subject Areas: Organometallic Chemistry, Materials Science, Porous Materia

An Amino-Functionalized Metal-Organic Framework, Based on a Rare Ba-12(COO)(18)(NO3)(2) Cluster, for Efficient C-3/C-2/C-1 Separation and Preferential Catalytic Performance

A barium(II) metal-organic framework (MOF) based on a predesigned amino-functionalized ligand, namely [Ba-2(L)(DMF)(H2O)(NO3)(1/3)]center dot DMF center dot EtOH center dot 2H(2)O (UPC-33) [H3L=4,4'-((2-amino-5-carboxy-1,3-phenylene)bis(ethyne-2,1-diyl))-dibenzoic acid] has been synthesized. UPC-33 is a 3-dimensional 3,18-connected network with fcu topology with a rare twelve-nuclear Ba-12(COO)(18)(NO3)(2) cluster. UPC-33 shows permanent porosity and a high adsorption heat of CO2 (49.92 kJ mol(-1)), which can be used as a platform for selective adsorption of CO2/CH4 (8.09). In addition, UPC-33 exhibits high separation selectivity for C-3 light hydrocarbons with respect to CH4 (228.34, 151.40 for C3H6/CH4, C3H8/CH4 at 273k and 1bar), as shown by single component gas sorption and selectivity calculations. Due to the existence of -NH2 groups in the channels, UPC-33 can effectively catalyze Knoevenagel condensation reactions with high yield, and substrate size and electron dependency

Asymmetric flavone-based liquid crystals: synthesis and properties

<p>A series of flavones (<b><i>n</i>-F</b>) substituted at the 4′, and 6 positions was prepared, characterised by NMR (¹H,¹³C), HRMS, and studied for liquid crystal properties. The 4′-alkoxy,6-methoxyflavones (<b>4-F–16-F</b>) exhibit varying ranges of nematic and smectic A phases as evidenced by polarised optical microscopy and differential scanning calorimetry (DSC). As the tail length is increased, the smectic phase becomes more prevalent. Smectic phases for (<b>8-F–16-F</b>) were further analysed by powder X-ray diffraction (XRD), and the rate of structural transformations was explored by combined DSC/XRD studies. Flavonol <b>6-F–OH</b> was also prepared but no mesogenic behaviour was observed. The molecular structures of <b>6-F</b> and <b>6-F–OH</b> were determined by single-crystal XRD and help to explain the differences in material properties. Additionally, fluorescence and electrochemical studies were conducted on solutions of <b><i>n</i>-F</b>.</p