Microporous Coordination Polymers: Exploring Heterogeneity with an Antimatter Probe.

Microporous coordination polymers (MCPs) are a rapidly growing class of porous, crystalline materials derived from alternating organic and inorganic building blocks. While some MCPs exhibit exceptional sorption properties, many others do not show the performance expected based on their crystallographic models. Realizing the full potential of these materials requires a thorough understanding of why many fall short of such expectation. Obtaining such insight is hampered by a lack of methods to examine localized defects and heterogeneity within these materials. This dissertation focuses on the use of positron annihilation lifetime spectroscopy (PALS) to elucidate the reasons for low porosity in two well-known MCPs, Zn-HKUST-1 and IRMOF-8. PALS is used to show that while the Zn-HKUST-1 interior contains empty pores of diameter commensurate with the corresponding crystallographic model, the pores near the surface of Zn-HKUST-1 are inaccessible, thereby precluding access to the porous interior. The porosity of the material before solvent removal is confirmed by the facile diffusion of solution-phase guest species into the crystal interior. IRMOF-8, despite having been first reported more than a decade ago, has until now shown surface areas at best only half of that expected based on its crystallographic model. A combination of PXRD, gas sorption, and PALS are used to show that typical preparations of IRMOF-8 in fact produce an interpenetrated analogue. A route to synthesize and activate non-interpenetrated IRMOF-8 is developed. The material has high gravimetric adsorption capacities for gaseous fuels such as hydrogen and methane; however, in situ PALS reveals that even at high pressures, only monolayer sorption is achievable with light gases above their critical temperatures. Hence, to maximize volumetric adsorption, linker functionalization is necessary. The use of PALS to analyze MCPs also resulted in the serendipitous discovery that positronium assumes a quantum mechanical Bloch state in highly ordered and porous MCPs such as IRMOF-1 and non-interpenetrated IRMOF-8.PHDMacromolecular Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99958/4/jfeldbly_1.pd

Panel Discussion: Provost\u27s Open Educational Resource (OER) Fellows

While the adoption of open educational resources (OERs) in the undergraduate curriculum has the evident benefit of reducing cost to the student, thinking deeply about OER adoption reveals numerous questions: can OERs match the quality of traditional textbooks and other commercial educational resources? Are there problems associated with the current textbook landscape that OERs can solve? And how easily can OERs be integrated into classrooms with established modes of instruction? Each of the Provost’s OER Fellows will discuss briefly some of the most important conclusions from the current OER research literature and discuss these in the context of SUNY Albany and its students. They will be sharing their experiences adopting and adapting OER materials for courses in the humanities and the sciences

Implementation of High School Level Laboratory Experiments Demonstrating Nanoscale Porosity in Metal–Organic Frameworks

Inorganic chemistry draws from many other disciplines of chemistry including organic, analytical, and physical chemistry, making it ideal for teaching foundational topics in high school and introductory undergraduate chemistry curricula. However, students rarely experience modern inorganic materials in introductory classes for a variety of reasons, including complexity of materials synthesis, expense of materials and instrumentation needed to analyze or demonstrate properties, and potential safety concerns. In this study, we use metal–organic frameworks (MOFs) as a modern class of materials that is both emblematic of the interdisciplinary nature of inorganic chemistry and capable of straightforward synthesis and application in introductory chemistry settings. We designed seven laboratory experiences for high school and new undergraduate students that include two MOF syntheses and five follow up gas and solution adsorption experiments. These experiments use low-toxicity reagents and solvents, can be carried out with minimal levels of expertise, and necessitate only common equipment such as laboratory balances and hot plates

Tunable Porosity and Conjugation in Ferrocene Polymers of Intrinsic Microporosity

Ferrocene (Fc) metallopolymers of intrinsic microporosity (MPIMs) have recently been reported as soluble, porous, non-network polymers, with evidence of electron delocalization along the polymer backbone. The combination of these properties makes Fc-MPIMs ideal candidate materials for optoelectronic devices, and the ability to tune these properties would broaden the impact of these materials. In this work, density functional theory (DFT) calculations at the CAM-B3LYP/def2SVP level were carried out on Fc MPIM fragments to examine the effect of pendant functional groups on conformational stability and electron delocalization in these systems. The conformational stability of the Fc MPIMs can affect the porosity, and the electronic delocalization is related to the conjugation in the material. The Fc MPIM fragments are most stable when the dihedral angle between Fc cyclopentadienyl (Cp) rings is 11.5°. Pendant functional groups are found to affect the stability of the local minimum at 144°, with alkyl chains increasing the stability, and bulky tert-butyl and trifluoromethyl groups decreasing stability. It is also possible to tune the electron delocalization of the HOMO and LUMO across the molecule. The Fe center of the Fc moiety contributes to the frontier orbitals, which is expected to enhance electronic communication in the parent polymer. Time-dependent density functional theory calculations indicate the π→π^* transition is slightly affected by the orientation of the dihedral angle between Cp rings, but primarily depends on the electronic nature of the pendant group. This work shows that the conformational stability and orbital delocalization of a model Fc MPIM can be tuned by functionalization with different pendant groups

Metal–Organic Frameworks for Fast Electrochemical Energy Storage: Mechanisms and Opportunities

Electrochemical energy storage devices are typically based on materials of inorganic nature which require high temperature synthesis and frequently feature scarce and/or toxic elements. Organic-based materials on the other hand can provide an attractive alternative, potentially yielding sustainable, safe, and cost-effective energy storage devices based on abundant elements (e.g. C, N, O, S, and H). However, attempts to incorporate organic and coordination compounds so far have led to sub-par cycling stability and charging rates due to insufficient structural and (electro)chemical stability, low electrical conductivity, and reduced performance at industrially relevant device scales. In recent years metal–organic frameworks (MOFs) have gained attention as having the potential to rival or even supersede traditional energy storage materials. Functional properties such as electronic or ionic conductivity can be incorporated into these materials by judicious design of their constituent inorganic and organic building blocks. However, full realization of the potential of MOFs for electrochemical energy storage requires joint expertise from distinct fields. In particular, bridges must be formed between electrochemists and synthetic and material chemists to establish the unified approach necessary to develop MOF-based energy storage devices exhibiting competitive performance

Probing the Edges between Stability and Degradation of a Series of ZnSe-Based Layered Hybrid Semiconductors

The discovery of layered materials with potentially unique electrical and chemical properties has become a major focus of materials research in the past decade. II-VI layered hybrids (LHs) are a family of ligand-protected layered materials capable of isolation in few-layer form and possess emissive and electronic properties of potential relevance to semiconductor device technologies. We showed previously that, akin to black phosphorus (BP) and transition metal dichalcogenides (TMDCs), II-VI LHs are sensitive to ambient atmospheric conditions. However, the causes for degradation of these ligand-protected materials remain unclear. Using ZnSe-based LHs, we show herein that the stability of these materials is related to the length and chemistry of the organic ligands coordinated to the LH surfaces. Furthermore, exposure to isotopically enriched H218O and 18O2 reveals that H2O and O2 are both reactants contributing to ZnSe-LH degradation. An H2O-initiated degradation pathway is proposed and is supported by density functional theory (DFT) calculations. Our findings contribute to the discovery of protection strategies for layered materials and elucidate a degradation pathway that may also be applicable to other layered materials

Photoresponse Characteristics of Archetypal Metal–Organic Frameworks

The photoelectrochemical responses of two archetypal metal–organic frameworks (MOFs), MOF-5 and MOF-177, have been assessed. Films of MOF-5 and MOF-177 were grown on carboxylic-acid-terminated conductive fluorine-doped tin oxide substrates. Separate analyses by powder X-ray diffraction, Raman spectroscopy, and fluorescence spectroscopy collectively indicated these films prepared via a solvothermal method in diethylformamide were free of residual impurities such as ZnO clusters and residual organics. Exposure of these films to white light illumination while immersed in acetonitrile electrolytes elicited measurable photocurrents. Wavelength-dependent analysis of the photoresponses showed that the measured photocurrents were induced by ultraviolet light and that the spectral response profiles followed closely the light absorption profiles of each respective material. Attenuation of the induced photocurrents was noted after prolonged ultraviolet light illumination and/or exposure of the films to H₂O(l), indicating that the observed photoresponse properties are directly related to the structural integrity of these MOFs. The cumulative data illustrate that such MOFs have innately light-sensitive properties that are atypical in high surface area materials

Ferrocene Metallopolymers of Intrinsic Microporosity (MPIMs)

We show here that non-network metallopolymers can possess intrinsic microporosity stemming from contortion introduced by metallocene building blocks. Metallopolymers constructed from ferrocenyl building blocks linked by phenyldiacetylene bridges are synthesized and possess BET surface areas up to 400 m2/g. As solubility imparted by pendant groups reduces porosity, copolymerization is used to simultaneously improve both accessible surface area and solubility. Spectroscopic analysis provides evidence that mixed valency between neighboring ferrocenyl units is supported in these polymers

Panel of Campus Advocates Speaking to Open Educational Resources at UAlbany

The University Faculty Senate passed a resolution on April 15th to formally recognize the use of open educational resources (OER) at the University at Albany and endorses that teaching faculty explore alternate learning materials and the possible adoption of OER as an important part of the University’s learning environment Soon thereafter, the Provost’s Office formed the OER Working Group made up of faculty, students, and University staff from Libraries, Advising, Registrar, Bookstore, UAS, IR, ITLAL and ETS. This panel, consisting of key OER Working Group stakeholders, will describe their accomplishments/ experiences with providing access to open educational resources at the University at Albany

Filling Pore Space in a Microporous Coordination Polymer to Improve Methane Storage Performance

A strategy that allows the tuning of pore size in microporous coordination polymers (MCPs) through modification of their organic linkers is presented. When large substituents are introduced onto the linker, these pendent groups partially occupy the pores, thus reducing pore size while serving as additional adsorption sites for gases. The approach takes advantage of the fact that, for methane storage materials, small pores (0.4–0.8 nm in diameter) are more desirable than large pores since small pores promote optimal volumetric capacity. This method was demonstrated with IRMOF-8, a MCP constructed from Zn₄O metal clusters and 2,6-naphthalenedicarboxylate (NDC) linkers. The NDC was functionalized through the addition of substituents including <i>tert</i>-butylethynyl or phenylethynyl groups. High pressure methane uptake demonstrates that the IRMOF-8 derivatives have significantly better performance than the unfunctionalized material in terms of both excess volumetric uptake and deliverable capacity. Moreover, IRMOF-8 derivatives also give rise to stronger interactions with methane molecules as shown by higher heat of adsorption values