In this work, we present a hierarchical approach to generate ferroelectric covalent frameworks based on rotatable polar groups. By using a multi-step workflow of increasing theoretical sophistication but also increasing computational costs, a unit cell with ferroelectric behavior can be generated for a given organic linker group. Starting with a basic point dipole model to find an appropriate unit cell, followed by a three-dimensional representation of the organic rotor, up to the full framework, each step confirms the desired attributes. This is achieved by using molecular dynamics and Monte Carlo Metropolis sampling in combination with the "Universal Force Field for Metall-Organic-Frameworks" (UFF4MOF) and the van der Waals corrected density functional tight-binding approach (known as GFN1-xTB) for the energy calculations. As a result, we demonstrate a covalent organic framework that is predicted to show a ferroelectric ground state that is stable up to temperatures beyond 100 K.

Abstract The complex mechanisms leading to degradation of a 3D-printed carbon short-fibre reinforced high-performance concrete which—due to the orientation of the carbon fibres—achieves very high tensile and flexural strengths, are investigated. For this purpose, multiple measurement methods acting on different scales were combined. At macro level, acoustic emission analysis and coda wave interferometry were used in cyclic, uniaxial tensile tests alongside conventional measurement methods such as digital image correlation to visualise internal damage. In addition, conductivity of the carbon fibres enabled conclusions to be drawn about the damage by measuring electric resistances. At micro and meso scale, the microstructure of unloaded specimens and development of microcracks were recorded in bending and in tension tests utilising computer tomography and microscopic examinations. Based on measurement data, microstructure-orientated unit cells allowing for the development of microcracks were derived and integrated into a computational homogenisation scheme capable of reproducing the material behaviour and relevant failure mechanisms.

The control of Jahn-Teller distortions in copper-based coordination polymers is crucial for tuning their magnetic and structural properties. Here, we report the synthesis and characterization of two novel Cu(II)-based metal-organic frameworks (MOFs), Cu(mta)2 and Cu(cta)2, derived from modified triazole ligands. By introducing steric bulk through methyl and cyclopentyl substituents, we systematically investigate the effect of lattice enlargement on local coordination environments and magnetic behaviour.Single-crystal and powder X-ray diffraction analyses reveal that Cu(mta)2 exhibits static Jahn-Teller distortions similar to those observed in Cu(ta)2, whereas Cu(cta)2 crystallizes in an undistorted, near-ideal cubic structure. Magnetic susceptibility and electron spin resonance measurements show strong antiferromagnetic interactions and temperature-dependent g-factor anisotropy for Cu(ta)2 and Cu(mta)2, while Cu(cta)2 displays nearly isotropic magnetic behavior and only dynamically JT distortions without a cooperative phase transition.These results demonstrate that steric ligand design offers a powerful strategy to modulate the interplay between lattice structure and magnetic anisotropy. Our findings provide fundamental insights into the suppression of cooperative static Jahn-Teller distortions and open pathways for the targeted design of multifunctional MOFs with tailored structural and magnetic properties.

Polynuclear metal complexes offer tunable electronic properties that are valuable for photocatalysis and molecular electronics. Herein, the synthesis and characterization of a poly-heteronuclear Kuratowski complex, [RuIICuI 4(Me2bta)6(PPh3)4] is presented. This complex is designed to investigate the electronic coupling between strongly reducing Cu(I) centers and a Ru(II) ion, mediated by a highly symmetric framework of triazolate ligands. Electrochemical studies reveal coupled redox behavior between Ru(II) and Cu(I), while UV-vis spectroscopy shows an overlapping Ru- and Cu-centered metal-to-ligand charge transfer (MLCT) band, redshifted in comparison to its {RuIIZnII 4} analog. Despite this, fluorescence lifetime measurements indicate that ultrafast nonradiative relaxation limits electron transfer between the metal centers. Density functional theory (DFT) and time-dependent-DFT calculations confirm that ligand-field effects, rather than direct Ru-Cu interactions, drive the MLCT redshift. These observations offer tentative insights into excited-state dynamics and highlight design aspects for controlling electronic communication in polynuclear systems.

A fine-grained UHPC, both undamaged and damaged by fatigue loading, was comparatively examined by various microstructural analytical methods, to evaluate the different techniques with respect to their applicability and relevance for the investigation of fatigue damage processes. The fatigue tests were stopped at the transition from phase II to phase III of the s-shaped strain development. The cyclic compression loading was performed with a frequency of ft = 1 Hz, and a stress level between Smin = 0.05 and Smax = 0.75 (fcm = 170.2 MPa). The fatigue process under these loading conditions is dominated by alterations and damages on the nano-scale, that can be observed by transmission electron microscopy. The resulting coarsening of the pore structure was also visible with dynamic vapor sorption. Nanoindentation indicates, that changes of the HD-C-S-H-phase occur. IR spectroscopy also indicates changes of the C-S-H phase and thermal analysis changes of the water content. Dynamic mechanical analysis (DMA) gave insight into the complex Young's modulus and Poisson's ratio changes. The acoustic emission technique gives information on the different processes during the single phases of fatigue and reveal a very different damage behaviour of dry and moist materials. Some microcracks are visible with light microscopy. It appears, that the number of cracks after fatigue is higher than before. With X-ray computed tomography, X-ray powder diffraction, the drying behaviour, the free water uptake, the water uptake under vacuum and by mercury intrusion porosimetry no significant differences between specimens with and without fatigue loading could be observed in this examination.

Efficient hydrogen isotope separation remains the biggest challenge due to the nearly identical physicochemical properties of H2 and D2. Through in situ neutron powder diffraction and gas adsorption experiments, we investigate the hydrogen isotopologue-induced structural dynamics of the triazole-based metal-organic framework [Mn(ta)2]. Gas loading induces a measurable lattice expansion, more pronounced for H2 than D2, and two distinct adsorption sites are identified with a subtle but significant difference in the occupancy of H2 and D2 at 60 K. Cryogenic thermal desorption spectroscopy after exposure to a 1:1 isotope mixture reveals an exceptionally high D2/H2 selectivity of 32.5 at 60 K. When exposed to a D2/H2 mixture of 5:95, D2 enriches to 75% in a single cycle. Given the commercial availability of the ligand and the scalability of the dia-framework topology across divalent transition metals, upscaling for industrial-scale deuterium separation is a realistic prospect. Our results give crucial molecular-level insights into isotopologue-induced structural dynamics in triazolate-based MOFs and provide guidance for improvement of isotope separation materials.

The synthesis, structure, and magnetic properties of a novel metal-organic framework (MOF), CFA-24 ([Cu6(dmta)9O(OH)]; H-dmta = 4,5-Dimethyl-1H-1,2,3-tri-azole), featuring alternating oxo-and hydroxo-bridged Cu (II) triangles are the focus of this study. The synthesis process of H-dmta and CFA-24 was optimized to ensure scalability and high yields, with the resulting MOF characterized using single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and various spectroscopic techniques. Structural analysis revealed a chiral cubic crystal system (space group P213), with copper ions forming equilateral triangles linked by triazoles. The study also explores the magnetic behaviour of CFA-24 using SQUID magnetometry and theoretical modeling. The magnetic data indicate strong antiferromagnetic interactions, modulated by Dzyaloshinskii-Moriya interactions (DMI), which contribute to the system's complex magnetic ground state. This research enhances the understanding of magnetically frustrated systems and positions CFA-24 as a potential candidate for spintronic applications.

Flexible metal-organic frameworks (FMOFs) with "S-shaped" stepped isotherms are stimuli-responsive smart materials that exhibit dynamic structural changes in response to guests, offering intrinsic thermal management and excellent regenerability compared to the classical rigid adsorbents. Herein, a 2-fold interpenetrated 3D flexible MOF (FMOF): IITKGP-39 is reported whose gate-opening behavior is synchronously intertwined with the pore functionalization strategy, which served as a fascinating tool for simultaneous redressal of highly demanding one-step ethylene (C2H4) purification via inverse ethane-ethylene (C2H6/C2H4) separation (i.e., C2H6 trapping) as well as acetylene-carbon dioxide (C2H2/CO2) separation through one-step sorbent separation technology (OSST). Notably, IITKGP-39 represents the first FMOF to exhibit inverse C2H6/C2H4 sorption behavior with outstanding breakthrough separation selectivity of ∼2.3 at room temperature (298 K), accompanied by one-step C2H4 purification from ternary C2 gas mixtures. Further, it excels in C2H2/CO2 separation with a remarkable uptake ratio of ∼18 and high breakthrough selectivity of 8.3. A detailed elucidation into structural dynamics is revealed through in situ X-ray diffraction analysis that manifested the sorbate-induced structural transformation among three distinct phases: as-synthesized (phase-α), activated (phase-β), and gas sorption/gate opened phase (phase-γ). Thus, IITKGP-39 is a unique industrially compatible two-in-one physisorbent that serves as a multipurpose molecular separator by virtue of reversible flexibility with outstanding separation performances.

Strategic design of solid-state proton-conducting electrolytes for application in anhydrous proton-exchange membrane fuel cells (PEMFCs) has gained burgeoning interest due to a spectrum of advantageous features, including higher CO tolerance and ease in the water management systems. Toward this direction, crystalline materials like metal-organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), and polyoxometalates (POMs) are emerging PEM materials, offering strategic structural engineering through crystallography, thus enabling ultrahigh anhydrous proton conductivity up to 10-2-10-1 S/cm. This Perspective highlights significant progress achieved thus far with such crystalline platforms in the domain of anhydrous proton conduction across a wide temperature window (sub-zero to above 100 °C). Based on their structural backgrounds, these platforms are categorized into four classes (viz. MOFs, COFs, HOFs, and POMs) with a detailed evolutionary timeline since their emergence early in 2009. Insightful discussions with a key focus on the strategies undertaken to attain anhydrous proton conductivity along with implementation in fuel cell technology through membrane electrode assembly are presented. A section on "Critical Analysis and Future Prospects" provides decisive key viewpoints on those overlooked issues with future endorsement (e.g., performance assessment with CO tolerance analysis and fuel cell test stand) for further development while comparing them with other anhydrous platforms from both academic and industrial perspectives.

We present the synthesis and comprehensive characterization of a series of complexes belonging to the Kuratowski (K3,3) family. These are pentanuclear {RuIIM4} complexes (M = Co2+, Ni2+, Zn2+) which were prepared by employing a directed two-step synthesis facilitated by the recently published [RuII(Me2bta)2(Me2btaH)4] precursor complex (Me2btaH = 5,6-dimethyl-1,2,3-benzotriazole). The pentanuclear Kuratowski complexes showcase a unique combination of photo-active ruthenium with redox-active metal centres. The μ3-bridging 1,2,3-triazolate ligands in these complexes facilitate electronic coupling between the metal centers, as revealed through electrochemical and photophysical studies. Comparisons with {RuIIZn4} and {RuIICu4} Kuratowski compounds reveal that Co(II) significantly influences both the Ru(II/III) redox step and the position of the MLCT (metal-to-ligand charge transfer) band, whereas Cu(II) and Ni(II) exhibit minimal influence. Photophysical investigations reveal the {RuIIZn4} compound as the only phosphorescent species, displaying an emission band extending into the near-infrared region. This emission originates from a triplet 3MLCT state and features an exceptionally large Stokes shift, with a long lifetime of the excited-state of about 3.3 μs in powdered form at room temperature.

We report a directed two-step synthesis toward pentanuclear Kuratowski complexes. First, six 5,6-dimethylbenzo[1,2,3]triazole ligands (Me(2)btaH) are coordinated to a single Ru(II) ion, providing a topologically ideal template for the addition of further metal ions. The synthesis and crystal structures of [RuCu4X4(Me(2)bta)(6)] [X = acetylacetonate (acac) and tris(3,5-dimethyl-1-pyrazolyl)borate (Tp*)] are described. Both represent new members of the family of so-called Kuratowski (K-3,K-3) complexes. The coordination units feature triazolato-bridged metal-centered {MM4} tetrahedra, which are known for frustrated magnetic interactions in both complexes and metal-organic frameworks. The novel Ru(II)-centered complexes were synthesized in order to investigate the influence of the presence or absence of a paramagnetic central metal ion in the Kuratowski complex. Superconducting quantum interference device and electron spin resonance measurements demonstrate that small deviations in bond lengths and valence angles can lead to the formation of pairs of magnetic exchange-coupled Cu(II) ions. Which Cu(II) ions pair up can be predicted in Jahn-Teller active compounds by the overlap of the respective orbitals. These data are compared with those gleaned for M(II)(ta)(2) (ta = 1,2,3-triazolate) lattices, in which structurally similar {MM4} tetrahedra constitute the secondary building units.

The widespread use and contamination of natural sources by new-generation drugs and pesticides have enhanced concern about environmental pollution. Understanding the above importance, we developed a superhydrophobic metal-organic framework (MOF) (SHMOF ': [Zr6O4(OH)(4)(BDC-NH-CO-R)(2.4)(BDC-NH2)(0.6)(CF3COO)(6)]2.5H(2)O4DMF) for ecological remediation via adsorption-based separation of hydrophobic drugs (flurbiprofen) and pesticides (fluazinam). The newly developed SHMOF ' has a high adsorption capacity toward flurbiprofen and fluazinam, i.e., 435 and 575 mg/g, respectively. The adsorption equilibrium time of the MOF is very short (15 and 10 min for flurbiprofen and fluazinam, respectively). The outstanding superhydrophobic nature of the MOF was employed to separate flurbiprofen and fluazinam from highly alkaline and acidic media and environmental water samples. The SHMOF ' has excellent selectivity toward the adsorption-based separation of flurbiprofen and fluazinam in the coexistence of common analytes. Again, we developed a polypropylene (PP) fabric-based composite of SHMOF ' (SHMOF '@PP) to separate the hydrophobic targeted analytes by using a zero-energy-consuming filtration-based separation method, which made this separation process cost-efficient and user-friendly. Moreover, Ag nanoparticles were doped to the superhydrophobic composite. The Ag-doped reusable SHMOF '@PP@Ag composite exhibited excellent bacterial antiadhesion and antibacterial properties toward Staphylococcus aureus bacteria.

The increasing utilization of hydrazine and its derivatives across diverse sectors highlights the pressing need for efficient detection methods to safeguard human health and the environment. Likewise, nicardipine, a widely used medication for heart diseases, necessitates accurate sensing techniques for clinical research and therapeutic monitoring. Here, we propose a novel approach using a naphthalimide-functionalized Zr-MOF as a fluorometric probe capable of detecting both hydrazine and nicardipine in aqueous medium. Our designed probe exhibited a significant 31-fold increase in fluorescence intensity upon interaction with hydrazine. At the same time, nicardipine induced 86% fluorescence quenching with an exceptionally rapid response time (100 s for hydrazine and 5 s for nicardipine). The designed probe has the ability to detect both analytes at nanomolar concentrations (LOD for hydrazine is 1.11 nM while that for nicardipine is 9.6 nM). Investigation across various wastewater samples and pH conditions further validated its practical utility. The mechanism behind fluorometric sensing of nicardipine was thoroughly investigated using modern instrumentation. Our study presents a versatile and effective approach for detecting hydrazine and nicardipine, addressing crucial needs in both industrial and biomedical contexts.

We report a directed two-step synthesis toward pentanuclear Kuratowski complexes. First, six 5,6-dimethylbenzo[1,2,3]triazole ligands (Me2btaH) are coordinated to a single Ru(II) ion, providing a topologically ideal template for the addition of further metal ions. The synthesis and crystal structures of [RuCu4X4(Me2bta)6] [X = acetylacetonate (acac) and tris(3,5-dimethyl-1-pyrazolyl)borate (Tp*)] are described. Both represent new members of the family of so-called Kuratowski (K3,3) complexes. The coordination units feature triazolato-bridged metal-centered {MM4} tetrahedra, which are known for frustrated magnetic interactions in both complexes and metal-organic frameworks. The novel Ru(II)-centered complexes were synthesized in order to investigate the influence of the presence or absence of a paramagnetic central metal ion in the Kuratowski complex. Superconducting quantum interference device and electron spin resonance measurements demonstrate that small deviations in bond lengths and valence angles can lead to the formation of pairs of magnetic exchange-coupled Cu(II) ions. Which Cu(II) ions pair up can be predicted in Jahn-Teller active compounds by the overlap of the respective orbitals. These data are compared with those gleaned for M(II)(ta)2 (ta = 1,2,3-triazolate) lattices, in which structurally similar {MM4} tetrahedra constitute the secondary building units.

Isostructural metal-organic frameworks (MOFs), namely MFU-4 and MFU-4-Br, in which the pore apertures are defined by anionic side ligands (Cl− and Br−, respectively), were synthesized and loaded with noble gases. By selecting the type of side ligand, one can fine-tune the pore aperture size, allowing for precise regulation of the entry and release of gas guests. In this study, we conducted experiments to examine gas loading and release using krypton and xenon as model gases, and we complemented our findings with computational modeling. Remarkably, the loaded gas guests remained trapped inside the pores even after being exposed to air under ambient conditions for extended periods, in some cases for up to several weeks. Therefore, we focused on determining the energy barrier preventing gas release using both theoretical and experimental methods. The results were compared in relation to the types of hosts and guests, providing valuable insights into the gas trapping process in MOFs, as well as programmed gas release in air under ambient conditions. Furthermore, the crystal structure of MFU-4-Br was elucidated using the three-dimensional electron diffraction (3DED) technique, and the bulk purity of the sample was subsequently verified through Rietveld refinement.

Enantioselective enrichment of R- or S-1-phenylethanol from racemic mixtures, reaching up to 42% enantiomeric excess and >60 wt% loading in the chiral CFA-22 (Coordination Framework Augsburg-22) metal-organic framework prepared from novel, scalable, and readily available camphor-based ligands, is demonstrated through single-crystal X-ray studies in conjunction with chiral high-performance liquid chromatography.

Isostructural metal-organic frameworks (MOFs), namely MFU-4 and MFU-4-Br, in which the pore apertures are defined by anionic side ligands (Cl- and Br-, respectively), were synthesized and loaded with noble gases. By selecting the type of side ligand, one can fine-tune the pore aperture size, allowing for precise regulation of the entry and release of gas guests. In this study, we conducted experiments to examine gas loading and release using krypton and xenon as model gases, and we complemented our findings with computational modeling. Remarkably, the loaded gas guests remained trapped inside the pores even after being exposed to air under ambient conditions for extended periods, in some cases for up to several weeks. Therefore, we focused on determining the energy barrier preventing gas release using both theoretical and experimental methods. The results were compared in relation to the types of hosts and guests, providing valuable insights into the gas trapping process in MOFs, as well as programmed gas release in air under ambient conditions. Furthermore, the crystal structure of MFU-4-Br was elucidated using the three-dimensional electron diffraction (3DED) technique, and the bulk purity of the sample was subsequently verified through Rietveld refinement.

The present study examines the potential coupling between dipolar dynamics and ionic charge transport in metal-organic framework (MOF) compounds. MOFs are known for their high porosity and customizable properties. By integrating freely rotating dipolar groups into the ligands, a novel structure, CFA-25, akin to the known BUT-2 framework, is synthesized. This facilitated the investigation of local and macroscopic effects, particularly the possible interplay between dipolar units and Cs cations. The research aimed to understand fundamental dipolar dynamics and ionic charge transport, employing Cs ions for their X-ray diffraction characterizability. Experimental analysis using dielectric spectroscopy, complemented by theoretical simulations, explored questions regarding glassy freezing of re-orientational dynamics, Cs cation motion within the network, and the influence of dipolar units on transport. Contrary to previous reports, this work finds that Cs transport exhibits substantial barriers, necessitating specialized simulation techniques for accurate characterization. This interdisciplinary approach sheds light on the intricate dynamics of MOFs and offers insights into their potential applications involving ion transport phenomena.