As three‐dimensional folding is prerequisite to biopolymer activity, complex functions may also be achieved through foldamer science. Because of the diversity of sizes, shapes and folding available with synthetic monomers, foldamer frameworks enable a numerous opportunities for designing new generations of catalysts. We herein demonstrate that heterocyclic γ‐peptide scaffolds represent a versatile platform for enamine catalysis. One central feature was to determine how the catalytic activity and the transfer of chiral information might be under the control of the conformational behaviours of the oligomer.

Polarized optical microscopy and spectroscopy are progressively becoming key methods for the high-throughput characterization of individual carbon nanotubes (CNTs) and other one-dimensional nanostructures, on substrate and in devices. The optical response of CNTs on substrate in cross polarization experiments is usually limited by the polarization conservation of the optical elements in the experimental setup. We developed a theoretical model taking into account the depolarization by the setup and the optical response of the substrate. We show that proper modelization of the experimental data requires to take into account both noncoherent and coherent light depolarization by the optical elements. We also show how the nanotube signal can be decoupled from the complex reflection factor of the antireflection substrate, which is commonly used to enhance the optical contrast. Finally, we describe an experimental protocol to extract the depolarization parameters and the complex nanotube susceptibility, and how it can improve the chirality assignment of individual carbon nanotubes in complex cases.

Over the past two decades significant efforts have been directed towards the elucidation of synthesis/structure/function correlations to guide the development of synthetic strategies for controlling the composition, size and shape of nanomaterials. In this context, organic–inorganic nanohybrids incorporating bridged silsesquioxanes have been of particular interest, due to their versatility and the structural control that can be achieved through independent modulation of the properties of the organic bridge and inorganic moieties. Such strategies have also been applied to the production of thin films on a variety of substrates, driven by the continuous need to develop new and enhanced materials with nanostructures engineered over multiple length scales for applications in electronics, optics, sensing, ferromagnetic, shape-selective membranes, etc. In this talk, I will first present a fundamental study of the nanostructuring mechanisms of model hybrid silica. Our experimental investigation was performed using an in operando approach (vibrational spectroscopies under pressure, light diffusion, microscopy) coupled with DFT calculations. Parameters controlling the evolution of the system during sol−gel processing: supramolecular interactions, hydrolysis, polycondensation, and nucleation and growth of the hybrid solid in solution were investigated. The relation between structural properties and applications will be then highlighted1-4.

We discuss the mechanism of the structural transformations of gas adsorbed in microporous crystalline solids. We show that it is possible to induce structural transformations in a confined system by simply varying the number of molecules adsorbed in the pore. We found that the mechanism of these novel, adsorption-induced structural transformation in nano-pores differs from the capillary condensation. First, the structure of the confined gas is determined by a competition between adsorption sites attractive forces and intermolecular interaction. Second, at low temperature, the transformation is discontinuous because it is defined by limited number of accessible adsorption sites [1,2]. In the case of methane adsorbed in IRMOFs porous structures the character of transformation depends on temperature but also on the IRMOF structure: it changes from strongly discontinuous (especially at low temperatures), to continuous transition. The mechanism of the transformation is also modified by the size of the gas molecules and the strength of interaction. However, even discontinuous transition can produce continuous isotherms. We will show that the continuous isotherm can be the effect of statistical dynamical switching between two phase, characterized by different number of adsorbed molecules. We show the simulated microscopic mechanism and experimental observations support such statistical interpretation. This work was supported by the Polish National Science Centre (NCN, grant no. 2015/17/B/ST8/00099). The calculations have been partially performed at the WCSS computer center of The Wroclaw University of Science and Technology, grant no 33.References[1] Heterogeneous melting of methane confined in nano-pores. Dundar, E.; Boulet, P.; Wexler, C.; et al. J. Chem. Phys. 145, 144704 (2016)[2] Adsorption-Induced Structural Phase Transformation in Nanopores. Kuchta, Bogdan; Dundar, Ege; Formalik, Filip; et al. Angewandte Chimie In. Ed. 56, 16243–16246. (2017)

Introduction/PurposeStorage and separation of gases are one of the most challenging processes when they have to be implemented at industrial scale. Hundreds of potential materials have been tested over the past years, especially for gas storage (hydrogen and methane for fueling applications) and separation of biogas (a mixture of 55 – 75% of methane 25 – 45% of carbon dioxide). Today, MOFs (Metal-Organic Frameworks) [1-2] are considered as the most promising materials for such applications. MOFs are hybrid, nanoporous materials with a very large surface area, in which pore sizes, shapes and adsorption energies can be almost unlimitedly tailored to fit the required adsorption characteristics.MethodsIn this work, we present simulations of methane and carbon dioxide adsorption in a wide range of MOF structures from CoRE-MOF database [3], and at variable content of humidity. Over 1000 structures have been tested using Grand Canonical Monte Carlo method (as implemented in RASPA code) to find the optimal material for the CH4/CO2 separation in conditions of increasing humidity.ResultsMOFs with pore limiting diameter (PLD) over 3.3 Å were chosen for the simulations. Due to the humid conditions, we chose structures from the middle range of hydrophilicity, kH between 5·10-2 mol/kg·Pa (CuBTC) and 5·10-6 mol/kg·Pa (ZIF-8). The initial screening allowed us to select the most promising structures for more detailed investigation. We show that 20 materials exhibit very promising selectivity (defined as the adsorbed amount of CO2­ to the amount of CH4) in the range from 100 to 900 and total uptake above 0.5 mol/kg.ConclusionsThe results provide clear information about different mechanisms of adsorption for selected structures. Furthermore, the adsorption of methane tends to be reduced with increasing humidity. Materials with a growing level of selectivity for CO2 and CH4 with increasing hydration degree are the most promising from the future application point of view.

Low frequency lattice vibrations (phonons) can be used as indicators of a variety of structural transformations. In particular, conformational changes in flexible metal-organic frameworks (MOFs) can be successfully explained by analyzing materials phonon spectrum in frequency range below 200 cm-1 [1,2]. It has been shown that such lattice vibrations are responsible for pressure- and adsorption-induced gate-opening in zeolitic imidazolate frameworks (ZIFs), and pore breathing in materials from MIL-53 family. In this work we present a phonon-based methodology to analyze MOFs deformations that can be detected in adsorption experiments but cannot be explained at the microscopic level without theoretical support based on numerical simulations.As a case study we have chosen to analyze adsorption-induced transformations in ZIF-8. The step-like adsorption isotherm observed in this material was interpreted in the literature as a signature of gate-opening (enlargement of the pore free volume) induced by the increasing number of guest molecules entering the pore. To analyze this phenomenon at the microscopic level, we first calculated and visualized normal modes of the lattice vibrations. For that, density functional theory (DFT) with PBE functional and empirical dispersion correction D3(BJ) was used. Only the modes which fulfill two criteria: (i) their frequency is below 200 cm-1, and (ii) the related lattice deformation leads to increase of the pore free volume, have been further analyzed. These deformed structures, (including one related to gate-opening, pore breathing and one which combines both deformations) were selected to serve as the adsorbent model. Grand Canonical Monte Carlo (GCMC) simulations have been performed to calculate the isotherms of adsorption in selected structures. Surprisingly, in the structure related to gate-opening, the mode, located at ~40 cm-1, and considered in the literature as the one responsible for step-like form of the isotherm did not provided an uptake larger than the undistorted structure. On the other hand, in the structure resulting from simultaneous pore breathing and gate-opening deformation the adsorption is significantly increased. Therefore, we consider that this deformation, induced by pore breathing and gate-opening phonons explains better the experimental observations..1. F. Formalik, et al., Microporous and Mesoporous Materials, (2018),2. M. R. Ryder, et al., Physical Review Letters, 113 (2014), 215502-21550