Tunable Negative Thermal Expansion in Layered Perovskite BaZrS.

We simulated the thermal expansion coefficient (TEC) of the layered perovskite sulfide BaZrS (4/ symmetry) from first principles. The calculated ambient pressure and room-temperature volumetric TEC is 38 × 10 K, which makes the material suitable for use in conventional PV devices. We further predicted low-temperature, pressure-tunable negative thermal expansion (NTE) in BaZrS that arises from a quasi-2D vibration mechanism shared by other = 2 Ruddlesden-Popper oxides CaTiO, CaZrO, and SrZrO.

Double-Walled Mesoporous Hydrogen-Bonded Organic Frameworks with High Methane Storage Capacity.

The development of mesoporous hydrogen-bonded organic frameworks (HOFs) is critically important for various applications, yet it poses significant challenges. Herein, we present the synthesis and characterization of a robust mesoporous HOF, RP-H200, constructed through the orchestration of π-π stacking and hydrogen bonding interactions in a 2-fold interpenetrated framework. RP-H200 features a unique double-walled structure with a pore size of 3.

Electronically Tunable Low-Valent Uranium Metallacarboranes.

Uranium metallocenes have played a pivotal role in advancing the understanding of low-valent uranium chemistry since the inception of this field, and they still find continued use today. Functionalization strategies for cyclopentadienyl (Cp) ligands used in uranium metallocenes have predominately focused on modifying the steric properties of the ligand through the incorporation of alkyl or silyl groups, which offer limited control over the electronic properties. Moreover, due to the flat, two-dimensional nature of Cp, functional groups will affect the coordination geometry of the uranium metallocene and can potentially present challenges in decoupling steric and electronic effects.

Charge Density Wave and Superconductivity in BaSbTeS Heterolayer Crystal with 2D Te Square Nets.

Low-dimensional materials with charge density waves (CDW) are attractive for their potential to exhibit superconductivity and nontrivial topological electronic features. Here we report the two-dimensional (2D) chalcogenide, BaSbTeS which acts as a new platform hosting these phenomena. The crystal structure of BaSbTeS is composed of alternating atomically thin Te square-net layers and double rock-salt type [(SbTeS)] slabs separated with Ba atoms.

Thorium metal-organic framework crystallization for efficient recovery from rare earth element mixtures.

Rare earth (RE) elements are critical materials that underpin many modern technologies, particularly in the clean energy industry. Despite their importance, these vital resources are difficult to obtain due to the presence of numerous metals and radioactive contaminants, such as thorium, that are present in RE ores. Current processing methods, which are dominated by homogeneous solvent extraction, are inefficient and produce substantial hazardous waste.

Interplay between Two Structure Types in the Incommensurately Modulated ATaSe Compounds (A = Rb, Cs).

Incommensurately modulated crystals are a rare class of materials that are notoriously difficult to characterize properly. We have synthesized two new incommensurately modulated compounds, RbTaSe and CsTaSe, based on the MQ (M = Nb, Ta; Q = S, Se) unit using high-temperature solid-state synthesis. Using superspace crystallography in combination with second harmonic generation measurements, we confirmed both materials to be noncentrosymmetric, falling into the superspace group 1(αβγ)0, while the basic cell suggests 2/.

Amidination of ligands for chemical and field-effect passivation stabilizes perovskite solar cells.

Surface passivation has driven the rapid increase in the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, state-of-the-art surface passivation techniques rely on ammonium ligands that suffer deprotonation under light and thermal stress. We developed a library of amidinium ligands, of interest for their resonance effect-enhanced N-H bonds that may resist deprotonation, to increase the thermal stability of passivation layers on perovskite surfaces.

Integrated CO Capture and Conversion by a Robust Cu(I)-Based Metal-Organic Framework.

Metal-organic frameworks (MOFs) have shown promise in both capturing CO under flue gas conditions and converting it into valuable chemicals. However, the development of a single MOF capable of capturing and selectively converting CO has remained elusive due to a lack of a harmonious combination of selectivity, water stability, and reactivity. For example, Cu(I)-based MOFs are particularly effective for CO conversion, but they do not typically exhibit selective CO adsorption and often suffer from instability in the presence of air and moisture.

Balancing volumetric and gravimetric capacity for hydrogen in supramolecular crystals.

The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both of which are essential for the efficient use of hydrogen as a fuel, is challenging. Here we report a controlled catenation strategy in hydrogen-bonded organic frameworks (RP-H100 and RP-H101) that depends on multiple hydrogen bonds to guide catenation in a point-contact manner, resulting in high volumetric and gravimetric surface areas, robustness and ideal pore diameters (~1.

Structural Evolution and Photoluminescence Quenching across the FASnIBr ( = 0-3) Perovskites.

One of the primary methods for band gap tuning in metal halide perovskites has been halide (I/Br) mixing. Despite widespread usage of this type of chemical substitution in perovskite photovoltaics, there is still little understanding of the structural impacts of halide alloying, with the assumption being the formation of ideal solid solutions. The FASnIBr ( = 0-3) family of compounds provides the first example where the assumption breaks down, as the composition space is broken into two unique regimes ( = 0-2.

Chemically Reversible CO Uptake by Dendrimer-Impregnated Metal-Organic Frameworks.

Industrialization over the past two centuries has resulted in a continuous rise in global CO emissions. These emissions are changing ecosystems and livelihoods. Therefore, methods are needed to capture these emissions from point sources and possibly from our atmosphere.

Nanotube Structure of AsPSSe ( = 0, 1).

Single-wall nanotubes of isostructural AsPSSe ( = 0, 1) are grown from solid-state reaction of stoichiometric amounts of the elements. The structure of AsPS was determined using single-crystal X-ray diffraction and refined in space group . The infinite, single-walled AsPS nanotubes have an outer diameter of ≈1.

Tailoring Hydrophobicity and Pore Environment in Physisorbents for Improved Carbon Dioxide Capture under High Humidity.

CALF-20, a Zn-triazolate-based metal-organic framework (MOF), is one of the most promising adsorbent materials for CO capture. However, competitive adsorption of water severely limits its performance when the relative humidity (RH) exceeds 40%, limiting the potential implementation of CALF-20 in practical settings where CO is saturated with moisture, such as postcombustion flue gas. In this work, three newly designed MOFs related to CALF-20, denoted as NU-220, CALF-20M-w, and CALF-20M-e that feature hydrophobic methyltriazolate linkers, are presented.

A Nanocavitation Approach to Understanding Water Capture, Water Release, and Framework Physical Stability in Hierarchically Porous MOFs.

Chemically stable metal-organic frameworks (MOFs) featuring interconnected hierarchical pores have proven to be promising for a remarkable variety of applications. Nevertheless, the framework's susceptibility to capillary-force-induced pore collapse, especially during water evacuation, has often limited practical applications. Methodologies capable of predicting the relative magnitudes of these forces as functions of the pore size, chemical composition of the pore walls, and fluid loading would be valuable for resolution of the pore collapse problem.

Rational Design and Reticulation of Infinite qbe Rod Secondary Building Units into Metal-Organic Frameworks through a Global Desymmetrization Approach for Inverse C H /C H Separation.

The development of reticular chemistry has enabled the construction of a large array of metal-organic frameworks (MOFs) with diverse net topologies and functions. However, dominating this class of materials are those built from discrete/finite secondary building units (SBUs), yet the designed synthesis of frameworks involving infinite rod-shaped SBUs remain underdeveloped. Here, by virtue of a global linker desymmetrization approach, we successfully targeted a novel Cu-MOF (Cu-ASY) incorporating infinite Cu-carboxylate rod SBUs with its structure determined by micro electron diffraction (MicroED) crystallography.

Modulator-Dependent Dynamics Synergistically Enabled Record SO Uptake in Zr(IV) Metal-Organic Frameworks Based on Pyrene-Cored Molecular Quadripod Ligand.

Developing innovative porous solid sorbents for the capture and storage of toxic SO is crucial for energy-efficient transportation and subsequent processing. Nonetheless, the quest for high-performance SO sorbents, characterized by exceptional uptake capacity, minimal regeneration energy requirements, and outstanding recyclability under ambient conditions, remains a significant challenge. In this study, we present the design of a unique tertiary amine-embedded, pyrene-based quadripod-shaped ligand.

Tuning Crystallinity and Stacking of Two-Dimensional Covalent Organic Frameworks through Side-Chain Interactions.

Two-dimensional covalent organic frameworks (2D COFs) form as layered 2D polymers whose sheets stack through high-surface-area, noncovalent interactions that can give rise to different interlayer arrangements. Manipulating the stacking of 2D COFs is crucial since it dictates the effective size and shape of the pores as well as the specific interactions between functional aromatic systems in adjacent layers, both of which will strongly influence the emergent properties of 2D COFs. However, principles for tuning layer stacking are not yet well understood, and many 2D COFs are disordered in the stacking direction.

Suitability of a diamine functionalized metal-organic framework for direct air capture.

The increase in the atmospheric carbon dioxide level is a significant threat to our planet, and therefore the selective removal of CO from the air is a global concern. Metal-organic frameworks (MOFs) are a class of porous materials that have shown exciting potential as adsorbents for CO capture due to their high surface area and tunable properties. Among several implemented technologies, direct air capture (DAC) using MOFs is a promising strategy for achieving climate targets as it has the potential to actively reduce the atmospheric CO concentration to a safer levels.

Cyclic versus Linear Alkylammonium Cations: Preventing Phase Transitions at Operational Temperatures in 2D Perovskites.

Two-dimensional lead halide perovskites offer numerous attractive features for optoelectronics owing to their soft, deformable lattices and high degree of chemical tunability. While alteration of the metal and halide ions gives rise to significant modification of the bandgap energy, the organic spacer cations offer in-roads to tuning phase behavior and more subtle functionalities in ways that remain to be understood. Here, we study six variations of 2D perovskites changing only the organic spacer cations and demonstrate that these components intrinsically impact material response in important ways such as altering crystallographic structure, temperature-induced phase transitions, and photoluminescence emission.

Unraveling the Role of Entropy in Thermoelectrics: Entropy-Stabilized Quintuple Rock Salt PbGeSnCdTe.

Entropy-engineered materials are garnering considerable attention owing to their excellent mechanical and transport properties, such as their high thermoelectric performance. However, understanding the effect of entropy on thermoelectrics remains a challenge. In this study, we used the PbGeSnCdTe family as a model system to systematically investigate the impact of entropy engineering on its crystal structure, microstructure evolution, and transport behavior.

Synthesis of the Candidate Topological Compound NiPb.

Spin-orbit coupling enables the realization of topologically nontrivial ground states. As spin-orbit coupling increases with increasing atomic number, compounds featuring heavy elements, such as lead, offer a pathway toward creating new topologically nontrivial materials. By employing a high-pressure flux synthesis method, we synthesized single crystals of NiPb, the first structurally characterized bulk binary phase in the Ni-Pb system.

2D Homologous Series SrFMBiS (M = Pb, AgBi; = 0, 1) and Commensurately Modulated SrFBiS.

We report three new mixed-anion two-dimensional (2D) compounds: SrFPbBiS, SrFAgBiS, and SrFBiS. Their structures as well as the parent compound SrFBiS were refined using single-crystal X-ray diffraction data, with the sequence of SrFBiS, SrFPbBiS, and SrFAgBiS defining the new homologous series SrFMBiS (M = Pb, AgBi; = 0, 1). SrFBiS has a different structure, which is modulated with a vector of 1/3* and was refined in superspace group 2/(0β0)00 as well as in the 1 × 3 × 1 superstructure with space group 2/ (with similar results).

Low Thermal Conductivity in Heteroanionic Materials with Layers of Homoleptic Polyhedra.

Although BiAgOSe, an analogue of a well-studied thermoelectric material BiCuOSe, is thermodynamically stable, its synthesis is complicated by the low driving force of formation from the stable binary and ternary intermediates. Here we have developed a "subtraction strategy" to suppress byproducts and produce pure phase BiAgOSe using hydrothermal methods. Electronic structure calculations and optical characterization show that BiAgOSe is an indirect bandgap semiconductor with a bandgap of 0.