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Magnesium-ion batteries (MIBs) are a "beyond Li-ion" technology that are hampered by Mg metal reactivity, which motivates the development of anode materials such as tin (Sn) with high theoretical capacity (903 mAh g -1 ). However, pure Sn is inactive for Mg 2+ storage. Herein, Mg alloying with Sn is enabled within dual-phase Bi-Sn anodes, where the optimal composition (Bi 66.5 Sn 33.5 ) outperformed single-phase Bi and Sn electrodes to deliver high specific capacity (462 mAh g -1 at 100 mA g -1 ), good cycle life (84% after 200 cycles), and significantly improved rate capability (403 mAh g -1 at 1000 mA g -1 ). Density functional theory (DFT) calculations revealed that Mg alloys first with Bi and the subsequent formation of the Mg 3 Bi 2 //Sn interfaces is energetically more favorable compared to the individual Mg 3 Bi 2 and Sn phases. Mg insertion into Sn is facilitated when Mg 3 Bi 2 is present. Moreover, dealloying Mg from Mg 3 Bi 2 :Mg 2 Sn systems requires the creation of Mg vacancies and subsequent Mg diffusion. Mg vacancy creation is easier for Mg 2 Sn compared to Mg 3 Bi 2 , while the latter has slightly lower activated Mg-diffusion pathways. The computational findings point toward easier magnesiation/demagnesiation for BiSn alloys over pure Bi or pure Sn, corroborating the superior Mg storage performance of Bi-Sn electrodes over the corresponding single-phase electrodes.

Electrolyzers operate over a range of temperatures; hence, it is crucial to design electrocatalysts that do not compromise the product distribution unless temperature can promote selectivity. This work reports a synthetic approach based on electrospinning to produce NiO:SnO 2 nanofibers (NFs) for selectively reducing CO 2 to formate above room temperature. The NFs comprise compact but disjoined NiO and SnO 2 nanocrystals identified with STEM. The results are attributed to the segregation of NiO and SnO 2 confirmed with XRD. The NFs are evaluated for the CO 2 reduction reaction (CO 2 RR) over various temperatures (25, 30, 35, and 40 °C). The highest faradaic efficiencies to formate (FE HCOO - ) are reached by NiO:SnO 2 NFs containing 50% of NiO and 50% SnO 2 (NiOSnO50NF), and 25% of NiO and 75% SnO 2 (NiOSnO75NF), at an electroreduction temperature of 40 °C. At 40 °C, product distribution is assessed with in situ differential electrochemical mass spectrometry (DEMS), recognizing methane and other species, like formate, hydrogen, and carbon monoxide, identified in an electrochemical flow cell. XPS and EELS unveiled the FE HCOO - variations due to a synergistic effect between Ni and Sn. DFT-based calculations reveal the superior thermodynamic stability of Ni-containing SnO 2 systems towards CO 2 RR over the pure oxide systems. Furthermore, computational surface Pourbaix diagrams showed that the presence of Ni as a surface dopant increases the reduction of the SnO 2 surface and enables the production of formate. Our results highlight the synergy between NiO and SnO 2 , which can promote the electroreduction of CO 2 at temperatures above room temperature., Competing Interests: The authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)

Semiconductor nanocrystals (NCs) are promising materials for various applications. Two of four recently identified Cu α Zn β Sn γ Se δ (CZTSe) domains demonstrate metallic character, while the other two exhibit semiconductor character. The presence of both metallic and semiconductor domains in one NC can hugely benefit future applications. In contrast to traditional band gap studies in the NC community, this study emphasizes that NC domain interfaces also affect the electronic properties. Specifically, the measured band gap of a tetrapod-shaped CZTSe NC is demonstrated to originate from two specific domains (tetragonal I 4 ¯ $\bar 4$ and monoclinic P1c1 Cu 2 ZnSnSe 4 ). The heterojunction between these two semiconductor domains exhibits a staggered type-II band alignment, facilitating the separation of photogenerated electron-hole pairs. Interestingly, tetrapod NCs have the potential to be efficient absorber materials with higher capacitance in photovoltaic applications due to the presence of both semiconductor/semiconductor interfaces and metal/semiconductor "Schottky"-junctions. For the two photo-absorbing domains, the calculated absorption spectra yield maximum photon-absorption coefficients of about 10 5 cm -1 in the visible and UV regions and a theoretical solar power conversion efficiency up to 20.8%. These insights into the structure-property relationships in CZTSe NCs will guide the design of more efficient advanced optical CZTSe materials for various applications., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Flexible metal-organic materials (FMOMs) with stepped isotherms can offer enhanced working capacity in storage applications such as adsorbed natural gas (ANG) storage. Unfortunately, whereas >1000 FMOMs are known, only a handful exhibit methane uptake of >150 cm 3 /cm 3 at 65 atm and 298 K, conditions relevant to ANG. Here, we report a double-walled 2-fold interpenetrated diamondoid ( dia ) network, X-dia-6-Ni, [Ni 2 L 4 (μ-H 2 O)] n , comprising a new azo linker ligand, L - ( L - = ( E )-3-(pyridin-4-yldiazenyl)benzoate) and 8-connected dinuclear molecular building blocks. X-dia-6-Ni exhibited gas (CO 2 , N 2 , CH 4 ) and liquid (C8 hydrocarbons)-induced reversible transformations between its activated narrow-pore β phase and γ , a large-pore phase with ca . 33% increase in unit cell volume. Single-crystal X-ray diffraction (SCXRD) studies of the as-synthesized phase α , β , and γ revealed that structural transformations were enabled by twisting of the azo moiety and/or deformation of the MBB. Further insight into these transformations was gained from variable temperature powder XRD and in situ variable pressure powder XRD. Low-temperature N 2 and CO 2 sorption revealed stepped Type F-II isotherms with saturation uptakes of 422 and 401 cm 3 /g, respectively. X-dia-6-Ni exhibited uptake of 200 cm 3 /cm 3 (65 atm, 298 K) and a high CH 4 working capacity of 166 cm 3 /cm 3 (5-65 bar, 298 K, 33 cycles), the third highest value yet reported for an FMOM and the highest value for an FMOM with a Type F-II isotherm.

Thanks to a hemilabile amide-based binding site, a previously unreported amide-functionalized metal-organic framework (MOF) exhibits high acetylene affinity over ethylene, methane, and carbon dioxide, three-in-one.

Coordination networks (CNs) that undergo guest-induced structural transformations are of topical interest thanks to their potential utility in separations and storage applications. Herein, we report a double diamondoid ( ddi ) topology CN, [Ni 2 (bimpz) 2 (bdc) 2 (H 2 O)] n or X-ddi-2-Ni (H 2 bdc = 1,4-benzenedicarboxylic acid, bimpz = 3,6-bis(imidazol-1-yl)pyridazine), that undergoes structural transformations induced by C8 isomers, i.e., xylenes ( o -xylene, OX; m -xylene, MX; p -xylene, PX) and ethylbenzene (EB). X-ddi-2-Ni was characterized by single-crystal to single-crystal transformations from a nonporous phase, X-ddi-2-Ni-β , to isostructural C8-loaded phases, namely X-ddi-2-Ni-OX, X-ddi-2-Ni-MX, X-ddi-2-Ni-PX and X-ddi-2-Ni-EB . X-ddi-2-Ni accommodates two C8 isomers per Ni unit, resulting in relatively high uptake (ca. 50 wt %), but with low selectivity toward C8 isomers as found using nuclear magnetic resonance (NMR) and gas chromatography (GC). In addition, a narrow range of gate-opening pressures for each isomer was determined from dynamic vapor sorption, consistent with the nonadaptable nature of the C8-loaded phase determined crystallographically, also supported by modeling., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice ( sql ) topology CN, X-sql-1-Cu , of formula [Cu(Imibz) 2 ] n (HImibz = {[4-(1 H -imidazol-1-yl)phenylimino]methyl}benzoic acid), isolated from the as-synthesized CN X-sql-1-Cu-(MeOH) 2 ·2MeOH , which subsequently transformed to a narrow pore solvate, X-sql-1-Cu-A·MeOH , upon mild activation (drying in air or heating at 333 K under nitrogen). X-sql-1-Cu-A·MeOH contains MeOH in cavities, which was removed through exposure to vacuum for 2 h, yielding the nonporous (closed) phase X-sql-1-Cu-A . In contrast, a more dense polymorph, X-sql-1-Cu-B , was obtained by exposing X-sql-1-Cu-(MeOH) 2 ·2MeOH directly to vacuum for 2 h. Gas sorption studies conducted on X-sql-1-Cu-A and X-sql-1-Cu-B revealed different switching behaviors to two open phases ( X-sql-1-Cu·CO 2 and X-sql-1-Cu·C 2 H 2 ), with different gate-opening threshold pressures for CO 2 at 195 K and C 2 H 2 at 278 K. Coincident CO 2 sorption and in situ powder X-ray diffraction studies at 195 K revealed that X-sql-1-Cu-A transformed to X-sql-1-Cu-B after the first sorption cycle and that the CO 2 -induced switching transformation was thereafter reversible. The results presented herein provide insights into the relationship between two polymorphs of a CN and the effect of polymorphism upon gas sorption properties. To the best of our knowledge, whereas sql networks such as X-sql-1-Cu are widely studied in terms of their structural and sorption properties, this study represents only the second example of an in-depth study of the sorption properties of polymorphic sql networks.

Semiconductor nanocrystals (NCs) with high elemental and structural complexity can be engineered to tailor for electronic, photovoltaic, thermoelectric, and battery applications etc. However, this greater complexity causes ambiguity in the atomic structure understanding. This in turn hinders the mechanistic studies of nucleation and growth, the theoretical calculations of functional properties, and the capability to extend functional design across complementary semiconductor nanocrystals. Herein, we successfully deciphered the atomic arrangements of 4 different nanocrystal domains in Cu α Zn β Sn γ Se δ (CZTSe) nanocrystals using crucial zone axis analysis on multiple crystals in different orientations. The results show that the essence of crystallographic progression from binary to multielemental semiconductors is actually the change of theoretical periodicity. This transition is caused by decreased symmetry in the crystal instead of previously assumed crystal deformation. We further reveal that these highly complex crystalline entities have highly ordered element arrangements as opposed to the previous understanding that their elemental orderings are random.

Hybrid ultramicroporous materials (HUMs), metal-organic platforms that incorporate inorganic pillars, are a promising class of porous solids. A key area of interest for such materials is gas separation, where HUMs have already established benchmark performances. Thanks to their ready compositional modularity, we report the design and synthesis of a new HUM, GEFSIX-21-Cu , incorporating the ligand pypz (4-(3,5-dimethyl-1 H -pyrazol-4-yl)pyridine, 21 ) and GeF 6 2- pillaring anions. GEFSIX-21-Cu delivers on two fronts: first, it displays an exceptionally high C 2 H 2 adsorption capacity (≥5 mmol g -1 ) which is paired with low uptake of CO 2 (<2 mmol g -1 ), and, second, a low enthalpy of adsorption for C 2 H 2 ( ca . 32 kJ mol -1 ). This combination is rarely seen in the C 2 H 2 selective physisorbents reported thus far, and not observed in related isostructural HUMs featuring pypz and other pillaring anions. Dynamic column breakthrough experiments for 1:1 and 2:1 C 2 H 2 /CO 2 mixtures revealed GEFSIX-21-Cu to selectively separate C 2 H 2 from CO 2 , yielding ≥99.99% CO 2 effluent purities. Temperature-programmed desorption experiments revealed full sorbent regeneration in <35 min at 60 °C, reinforcing HUMs as potentially technologically relevant materials for strategic gas separations.

High and increasing production of separation of C8 aromatic isomers demands the development of purification methods that are efficient, scalable, and inexpensive, especially for p -xylene, PX, the largest volume C8 commodity. Herein, we report that 4-(1 H -1,2,4-triazol-1-yl)-phenyl-1 H -benzo[de]isoquinoline-1,3(2H)-dione ( TPBD ), a molecular compound that can be prepared and scaled up via solid-state synthesis, exhibits exceptional PX selectivity over each of the other C8 isomers, o -xylene (OX), m -xylene (MX), and ethylbenzene (EB). The apohost or α form of TPBD was found to exhibit conformational polymorphism in the solid state enabled by rotation of its triazole and benzene rings. TPBD-αI and TPBD-αII are nonporous polymorphs that transformed to the same PX inclusion compound, TPBD-PX , upon contact with liquid PX. TPBD enabled highly selective capture of PX, as established by competitive slurry experiments involving various molar ratios in binary, ternary, and quaternary mixtures of C8 aromatics. Binary selectivity values for PX as determined by 1 H NMR spectroscopy and gas chromatography ranged from 22.4 to 108.4, setting new benchmarks for both PX/MX (70.3) and PX/EB (59.9) selectivity as well as close to benchmark selectivity for PX/OX (108.4). To our knowledge, TPBD is the first material of any class to exhibit such high across-the-board PX selectivity from quaternary mixtures of C8 aromatics under ambient conditions. Crystallographic and computational studies provide structural insight into the PX binding site in TPBD-PX , whereas thermal stability and capture kinetics were determined by variable-temperature powder X-ray diffraction and slurry tests, respectively. That TPBD offers benchmark PX selectivity and facile recyclability makes it a prototypal molecular compound for PX purification or capture under ambient conditions.

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF 6 )(L) 2 ] n , (L=1,4-bis(1-imidazolyl)benzene, SiF 6 2- =SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-Cu N , [Cu(SiF 6 )(L N ) 2 ] n (L N =2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO 2 . As-synthesized SIFSIX-23-Cu N , α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N 2 (77 K), rather it reverted to α induced by CO 2 at 195, 273 and 298 K. CO 2 desorption resulted in α', a shape-memory phase which subsequently exhibited type-I isotherms for N 2 (77 K) and CO 2 as well as strong performance for separation of CO 2 /N 2 (15/85) at 298 K and 1 bar driven by strong binding (Q st =45-51 kJ/mol) and excellent CO 2 /N 2 selectivity (up to 700). Interestingly, α' reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-Cu N ., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

This paper studies the anticancer potency of dendritic poly(aryl ether)-substituted polypyridyl ligand-based ruthenium(II) coordination entities. The dendritic coordination entities were successfully designed, synthesized, and characterized by different spectral methods such as Fourier transform infrared (FTIR), 1 H and 13 C- NMR, and mass spectrometry. Further, to understand the structure and solvation behavior of the coordination entities, we performed all-atom molecular dynamics (MD) simulations. The behavior, configuration, and size of the coordination entities in DMSO and water were studied by calculating the radius of gyration ( R g ) and solvent-accessible surface area (SASA). The MTT assay was used to assess the in vitro cytotoxicity of all of the coordination entities against cancerous A549 (lung cancer cells), MDA MB 231 (breast cancer cells), and HepG2 (liver cancer cells) and was found to be good with comparable IC 50 values with respect to the standard drug cisplatin. The coordination entities exhibited dose dependence, and the highest activity was shown against HepG2 cell lines in comparison to the other cancer cell lines. In addition, fluorescence staining studies, such as AO/EB, DAPI, and cell death analysis by PI staining, were performed on the coordination entities to understand the apoptosis mechanism. Furthermore, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) assays confirmed apoptosis in cancer cells via the mitochondrial pathway. The DNA fragmentation assay was done followed by molecular docking analysis with DNA executed to strengthen and support the experimental observations.

The metal-organic framework (MOF) Hf-DUT-52 was prepared with diamino functionality by the solvothermal method. This material displayed fluorometric sensing ability toward a nerve agent simulant (diethyl chlorophosphate (DCP)) and 3-diethylaminophenol (3-DEAP). It is the first-ever reported fluorescent MOF sensor for DCP and 3-DEAP. Apart from a fast response (<5 s), the sensor had a very low detection limit for both DCP and DEAP (limit of detection (LOD) values for DCP and 3-DEAP sensing were 9 and 125 nM, respectively). The obtained detection limit is the second lowest among all of the reported optical sensors for DCP. The sensor also displayed its capability to identify the presence of trace amount of DCP in various natural water specimens with good selectivity. Moreover, MOF@cotton composites were developed for visual, on-site, nanomolar-level detection of both targeted analytes. Furthermore, a MOF@PVA thin film was fabricated and successfully utilized for the detection of highly volatile and deadly poisonous DCP in the vapor phase. The sensor was also recyclable for up to five cycles without losing appreciable efficiency. Density functional theory (DFT)-based periodic and cluster calculations were performed to shed light on the sensing ability of the MOF by studying the interactions of DCP and DEAP with the MOF. Our theoretical results reveal the importance of linker defects and water chemisorption on the adsorption/complexation of the analytes at uncoordinated Hf sites.

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu , a new variant of a previously reported ultramicroporous square lattice, sql , topology material, sql-SIFSIX-bpe-Zn , can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA ( AA ) and sql-NbOFFIVE-bpe-Cu-AB ( AB ), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA ( AA ) is isostructural with sql-SIFSIX-bpe-Zn , each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB ( AB ) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C 3 H 4 /C 3 H 6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C 3 H 4 /C 3 H 6 selectivity (270) and a new benchmark for productivity (118 mmol g -1 ) of polymer grade C 3 H 6 (purity > 99.99%) from a 1:99 C 3 H 4 /C 3 H 6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C 3 H 4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C 3 H 4 and C 3 H 6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Metal complexes are extensively explored as catalysts for oxidation reactions; molecular-based mechanisms are usually proposed for such reactions. However, the roles of the decomposition products of these materials in the catalytic process have yet to be considered for these reactions. Herein, the cyclohexene oxidation in the presence of manganese(III) 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine chloride tetrakis(methochloride) (1) in a heterogeneous system via loading the complex on an SBA-15 substrate is performed as a study case. A molecular-based mechanism is usually suggested for such a metal complex. Herein, 1 was selected and investigated under the oxidation reaction by iodosylbenzene or (diacetoxyiodo)benzene (PhI(OAc) 2 ). In addition to 1, at least one of the decomposition products of 1 formed during the oxidation reaction could be considered a candidate to catalyze the reaction. First-principles calculations show that Mn dissolution is energetically feasible in the presence of iodosylbenzene and trace amounts of water., (© 2023. The Author(s).)

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] n ( X-dia-4-Co ) and [Co(bimbz)(bdc)] n ( X-dia-5-Co ) (H 2 bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their N -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO 2 , whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P / P 0 ≈ 0.008 or P ≈ 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

A molecular porous material, MPM-2, comprised of cationic [Ni 2 (AlF 6 )(pzH) 8 (H 2 O) 2 ] and anionic [Ni 2 Al 2 F 11 (pzH) 8 (H 2 O) 2 ] complexes that generate a charge-assisted hydrogen-bonded network with pcu topology is reported. The packing in MPM-2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM-2 is found to exhibit excellent stability in water (>1 year). Unlike most hydrogen-bonded organic frameworks which typically show poor stability in organic solvents, MPM-2 exhibited excellent stability with respect to various organic solvents for at least two days. MPM-2 is found to be permanently porous with gas sorption isotherms at 298 K revealing a strong affinity for C 2 H 2 over CO 2 thanks to a high (ΔQ st ) AC [Q st (C 2 H 2 ) - Q st (CO 2 )] of 13.7 kJ mol -1 at low coverage. Dynamic column breakthrough experiments on MPM-2 demonstrated the separation of C 2 H 2 from a 1:1 C 2 H 2 /CO 2 mixture at 298 K with effluent CO 2 purity of 99.995% and C 2 H 2 purity of >95% after temperature-programmed desorption. C-H···F interactions between C 2 H 2 molecules and F atoms of AlF 6 3- are found to enable high selectivity toward C 2 H 2 , as determined by density functional theory simulations., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Drug delivery platforms are anticipated to have biocompatible and bioinert surfaces. PEGylation of drug carriers is the most approved method since it improves water solubility and colloid stability and decreases the drug vehicles' interactions with blood components. Although this approach extends their biocompatibility, biorecognition mechanisms prevent them from biodistribution and thus efficient drug transfer. Recent studies have shown (poly)zwitterions to be alternatives for PEG with superior biocompatibility. (Poly)zwitterions are super hydrophilic, mainly stimuli-responsive, easy to functionalize and they display an extremely low protein adsorption and long biodistribution time. These unique characteristics make them already promising candidates as drug delivery carriers. Furthermore, since they have highly dense charged groups with opposite signs, (poly)zwitterions are intensely hydrated under physiological conditions. This exceptional hydration potential makes them ideal for the design of therapeutic vehicles with antifouling capability, i.e ., preventing undesired sorption of biologics from the human body in the drug delivery vehicle. Therefore, (poly)zwitterionic materials have been broadly applied in stimuli-responsive "intelligent" drug delivery systems as well as tumor-targeting carriers because of their excellent biocompatibility, low cytotoxicity, insignificant immunogenicity, high stability, and long circulation time. To tailor (poly)zwitterionic drug vehicles, an interpretation of the structural and stimuli-responsive behavior of this type of polymer is essential. To this end, a direct study of molecular-level interactions, orientations, configurations, and physicochemical properties of (poly)zwitterions is required, which can be achieved via molecular modeling, which has become an influential tool for discovering new materials and understanding diverse material phenomena. As the essential bridge between science and engineering, molecular simulations enable the fundamental understanding of the encapsulation and release behavior of intelligent drug-loaded (poly)zwitterion nanoparticles and can help us to systematically design their next generations. When combined with experiments, modeling can make quantitative predictions. This perspective article aims to illustrate key recent developments in (poly)zwitterion-based drug delivery systems. We summarize how to use predictive multiscale molecular modeling techniques to successfully boost the development of intelligent multifunctional (poly)zwitterions-based systems., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Photocatalytic H 2 generation by water splitting is a promising alternative for producing renewable fuels. This work synthesized a new type of Ta 2 O 5 /SrZrO 3 heterostructure with Ru and Cu (RuO 2 /Cu x O/Ta 2 O 5 /SrZrO 3 ) using solid-state chemistry methods to achieve a high H 2 production of 5164 μmol g -1 h -1 under simulated solar light, 39 times higher than that produced using SrZrO 3 . The heterostructure performance is compared with other Ta 2 O 5 /SrZrO 3 heterostructure compositions loaded with RuO 2 , Cu x O, or Pt. Cu x O is used to showcase the usage of less costly cocatalysts to produce H 2 . The photocatalytic activity toward H 2 by the RuO 2 /Cu x O/Ta 2 O 5 /SrZrO 3 heterostructure remains the highest, followed by RuO 2 /Ta 2 O 5 /SrZrO 3 > Cu x O/Ta 2 O 5 /SrZrO 3 > Pt/Ta 2 O 5 /SrZrO 3 > Ta 2 O 5 /SrZrO 3 > SrZrO 3 . Band gap tunability and high optical absorbance in the visible region are more prominent for the heterostructures containing cocatalysts (RuO 2 or Cu x O) and are even higher for the binary catalyst (RuO 2 /Cu x O). The presence of the binary catalyst is observed to impact the charge carrier transport in Ta 2 O 5 /SrZrO 3 , improving the solar to hydrogen conversion efficiency. The results represent a valuable contribution to the design of SrZrO 3 -based heterostructures for photocatalytic H 2 production by solar water splitting.

The structure-activity relationship is a cornerstone topic in catalysis, which lays the foundation for the design and functionalization of catalytic materials. Of particular interest is the catalysis of the hydrogen evolution reaction (HER) by palladium (Pd), which is envisioned to play a major role in realizing a hydrogen-based economy. Interestingly, experimentalists observed excess heat generation in such systems, which became known as the debated "cold fusion" phenomenon. Despite the considerable attention on this report, more fundamental knowledge, such as the impact of the formation of bulk Pd hydrides on the nature of active sites and the HER activity, remains largely unexplored. In this work, classical electrochemical experiments performed on model Pd(hkl) surfaces, "noise" electrochemical scanning tunneling microscopy (n-EC-STM), and density functional theory are combined to elucidate the nature of active sites for the HER. Results reveal an activity trend following Pd(111) > Pd(110) > Pd(100) and that the formation of subsurface hydride layers causes morphological changes and strain, which affect the HER activity and the nature of active sites. These findings provide significant insights into the role of subsurface hydride formation on the structure-activity relations toward the design of efficient Pd-based nanocatalysts for the HER., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Hybrid ultramicroporous materials, HUMs, are comprised of metal cations linked by combinations of inorganic and organic ligands. Their modular nature makes them amenable to crystal engineering studies, which have thus far afforded four HUM platforms (as classified by the inorganic linkers). HUMs are of practical interest because of their benchmark gas separation performance for several industrial gas mixtures. We report herein design and gram-scale synthesis of the prototypal sulfate-linked HUM, the fsc topology coordination network ([Zn(tepb)(SO 4 )] n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C 2 H 2 via O⋅⋅⋅HC interactions but weak CO 2 binding, affording a new benchmark for the difference between C 2 H 2 and CO 2 heats of sorption at low loading (ΔQ st =24 kJ mol -1 ). Dynamic column breakthrough studies afforded fuel-grade C 2 H 2 from trace (1 : 99) or 1 : 1 C 2 H 2 /CO 2 mixtures, outperforming its SiF 6 2- analogue, SIFSIX-22-Zn., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

So far, many studies on the oxygen-evolution reaction (OER) by Mn oxides have been focused on activity; however, the identification of the best performing active site and corresponding catalytic cycles is also of critical importance. Herein, the real intrinsic activity of layered Mn oxide toward OER in Fe/Ni-free KOH is studied for the first time. At pH ≈ 14, the onset of OER for layered Mn oxide in the presence of Fe/Ni-free KOH happens at 1.72 V (vs reversible hydrogen electrode (RHE)). In the presence of Fe ions, a 190 mV decrease in the overpotential of OER was recorded for layered Mn oxide as well as a significant decrease (from 172.8 to 49 mV/decade) in the Tafel slope. Furthermore, we find that both Ni and Fe ions increase OER remarkably in the presence of layered Mn oxide, but that pure layered Mn oxide is not an efficient catalyst for OER without Ni and Fe under alkaline conditions. Thus, pure layered Mn oxide and electrolytes are critical factors in finding the real intrinsic activity of layered Mn oxide for OER. Our results call into question the high efficiency of layered Mn oxides toward OER under alkaline conditions and also elucidate the significant role of Ni and Fe impurities in the electrolyte in the presence of layered Mn oxide toward OER under alkaline conditions. Overall, a computational model supports the conclusions from the experimental structural and electrochemical characterizations. In particular, substitutional doping with Fe decreases the thermodynamic OER overpotential up to 310 mV. Besides, the thermodynamic OER onset potential calculated for the Fe-free structures is higher than 1.7 V (vs RHE) and, thus, not in the stability range of Mn oxides.

The trade-off between selectivity and adsorption capacity with porous materials is a major roadblock to reducing the energy footprint of gas separation technologies. To address this matter, we report herein a systematic crystal engineering study of C 2 H 2 removal from CO 2 in a family of hybrid ultramicroporous materials (HUMs). The HUMs are composed of the same organic linker ligand, 4-(3,5-dimethyl-1 H -pyrazol-4-yl)pyridine, pypz, three inorganic pillar ligands, and two metal cations, thereby affording six isostructural pcu topology HUMs. All six HUMs exhibited strong binding sites for C 2 H 2 and weaker affinity for CO 2 . The tuning of pore size and chemistry enabled by crystal engineering resulted in benchmark C 2 H 2 /CO 2 separation performance. Fixed-bed dynamic column breakthrough experiments for an equimolar (v/v = 1:1) C 2 H 2 /CO 2 binary gas mixture revealed that one sorbent, SIFSIX-21-Ni, was the first C 2 H 2 selective sorbent that combines exceptional separation selectivity (27.7) with high adsorption capacity (4 mmol·g -1 )., Competing Interests: The authors declare no competing interests., (© 2021 The Authors.)

Unlike most gases, acetylene storage is a challenge because of its inherent pressure sensitivity. Herein, a square lattice ( sql ) coordination network [Cu(4,4'-bipyridine) 2 (BF 4 ) 2 ] n ( sql-1-Cu-BF 4 ) is investigated with respect to its C 2 H 2 sorption behavior from 189 to 298 K. The C 2 H 2 sorption studies revealed that sql-1-Cu-BF 4 exhibits multistep isotherms that are temperature-dependent and consistent with the transformation from "closed" (nonporous) to four "open" (porous) phases induced by the C 2 H 2 uptake. The Clausius-Clapeyron equation was used to calculate the performance of sql-1-Cu-BF 4 for C 2 H 2 storage at pressures >1 bar, which revealed that its volumetric working capacity at 288 K is slightly superior to acetone (174 vs 170 cm 3 cm -3 ) over a safer pressure range (1-3.5 vs 1-15 bar). Molecular simulations provided insights into the observed switching phenomena, revealing that the layer expansion of sql-1-Cu-BF 4 occurs via intercalation and inclusion of C 2 H 2 . These results indicate that switching adsorbent layered materials offer promise for utility in the context of C 2 H 2 storage and delivery.

Herein, we investigate the oxygen-evolution reaction (OER) and electrochemistry of a Pd foil in the presence of iron under alkaline conditions (pH ≈ 13). As a source of iron, K 2 FeO 4 is employed, which is soluble under alkaline conditions in contrast to many other Fe salts. Immediately after reacting with the Pd foil, [FeO 4 ] 2- causes a significant increase in OER and changes in the electrochemistry of Pd. In the absence of this Fe source and under OER, Pd(IV) is stable, and hole accumulation occurs, while in the presence of Fe this accumulation of stored charges can be used for OER. A Density Functional Theory (DFT) based thermodynamic model suggests an oxygen bridge vacancy as an active site on the surface of PdO 2 and an OER overpotential of 0.42 V. A substitution of Pd with Fe at this active site reduces the calculated OER overpotential to 0.35 V. The 70 mV decrease in overpotential is in good agreement with the experimentally measured decrease of 60 mV in the onset potential. In the presence of small amounts of Fe salt, our results point toward the Fe doping of PdO 2 rather than extra framework FeO x (Fe(OH) 3 , FeO(OH), and KFeO 2 ) species on top of PdO 2 as the active OER sites.

The sluggish kinetics of the oxygen evolution reaction (OER) at the anode severely limit hydrogen production at the cathode in water splitting systems. Although electrocatalytic systems based on cheap and earth-abundant copper catalysts have shown promise for water oxidation under basic conditions, only very few examples with high overpotential can be operated under acidic or neutral conditions, even though hydrogen evolution in the latter case is much easier. This work presents an efficient and robust Cu-based molecular catalyst, which self-assembles as a periodic film from its precursors under aqueous conditions on the surface of a glassy carbon electrode. This film catalyzes the OER under neutral conditions with impressively low overpotential. In controlled potential electrolysis, a stable catalytic current of 1.0 mA cm -2 can be achieved at only 2.0 V (vs. RHE) and no significant decrease in the catalytic current is observed even after prolonged bulk electrolysis. The catalyst displays first-order kinetics and a single site mechanism for water oxidation with a TOF (k cat ) of 0.6 s -1 . DFT calculations on of the periodic Cu(TCA) 2 (HTCA=1-mesityl-1H-1,2,3-triazole-4-carboxylic acid) film reveal that TCA defects within the film create Cu I active sites that provide a low overpotential route for OER, which involves Cu I , Cu II -OH, Cu III =O and Cu II -OOH intermediates and is enabled at a potential of 1.54 V (vs. RHE), requiring an overpotential of 0.31 V. This corresponds well with an overpotential of approximately 0.29 V obtained experimentally for the grown catalytic film after 100 CV cycles at pH 6. However, to reach a higher current density of 1 mA cm -2 , an overpotential of 0.72 V is required., (© 2020 Wiley-VCH GmbH.)

Ambient-pressure operando soft X-ray absorption spectroscopy (soft-XAS) was applied to study the reactivity of hydroxylated SnO 2 nanoparticles toward reducing gases. H 2 was first used as a test case, showing that the gas phase and surface states can be simultaneously probed: Soft-XAS at the O K-edge gains sensitivity toward the gas phase, while at the Sn M 4,5 -edges, tin surface states are explicitly probed. Results obtained by flowing hydrocarbons (CH 4 and CH 3 CHCH 2 ) unequivocally show that these gases react with surface hydroxyl groups to produce water without producing carbon oxides and release electrons that localize on Sn to eventually form SnO. The partially reduced SnO 2 -  x layer at the surface of SnO 2 is readily reoxidized to SnO 2 by treating the sample with O 2 at mild temperatures (>200 °C), revealing the nature of "electron sponge" of tin oxide. The experiments, combined with DFT calculations, allowed devising of a mechanism for dissociative hydrocarbon adsorption on SnO 2 , involving direct reduction of Sn sites at the surface via cleavage of C-H bonds and the formation of methoxy- and/or methyl-tin species at the surface., Competing Interests: The authors declare no competing financial interest.

Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF 6 2- -pillared square grid material, [Cu(SiF 6 )(L) 2 ] n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu . SIFSIX-23-Cu exhibits reversible switching between nonporous ( β1 ) and several porous ( α , γ1 , γ2 , and γ3 ) phases triggered by exposure to N 2 , CO 2 , or H 2 O. In addition, heating β1 to 433 K resulted in irreversible transformation to a closed polymorph, β2 . Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol -1 ) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO 2 uptake (ca. 216 cm 3 /g at 195 K), and good thermal stability.

Water splitting is the key step towards artificial photosystems for solar energy conversion and storage in the form of chemical bonding. The oxidation of water is the bottle-neck of this process that hampers its practical utility; hence, efficient, robust, and easy to make catalytic systems based on cheap and earth-abundant materials are of exceptional importance. Herein, an in situ generated cobalt catalyst, [Co II (TCA) 2 (H 2 O) 2 ] (TCA=1-mesityl-1,2,3-1H-triazole-4-carboxylate), that efficiently conducts photochemical water oxidation under near-neutral conditions is presented. The catalyst showed high stability under photolytic conditions for more than 3 h of photoirradiation. During electrochemical water oxidation, the catalytic system assembled a catalyst film, which proved not to be cobalt oxide/hydroxide as normally expected, but instead, and for the first time, generated a molecular cobalt complex that incorporated the organic ligand bound to cobalt ions. The catalyst film exhibited a low overpotential for electrocatalytic water oxidation (360 mV) and high oxygen evolution peak current densities of 9 and 2.7 mA cm -2 on glassy carbon and indium-doped tin oxide electrodes, respectively, at only 1.49 and 1.39 V (versus a normal hydrogen electrode), respectively, under neutral conditions. This finding, exemplified on the in situ generated cobalt complex, might be applicable to other molecular systems and suggests that the formation of a catalytic film in electrochemical water oxidation experiments is not always an indication of catalyst decomposition and the formation of nanoparticles., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanoscale Zr-based metal organic frameworks (MOFs) UiO-66 and UiO-67 were studied as potential anticancer drug delivery vehicles. Two model drugs were used, hydrophobic paclitaxel and hydrophilic cisplatin, and were adsorbed onto/into the nano MOFs (NMOFs). The drug loaded MOFs were further encapsulated inside a modified poly(ε-caprolactone) with d-α-tocopheryl polyethylene glycol succinate polymeric matrix, in the form of microparticles, in order to prepare sustained release formulations and to reduce the drug toxicity. The drugs physical state and release rate was studied at 37°C using Simulated Body Fluid. It was found that the drug release depends on the interaction between the MOFs and the drugs while the controlled release rates can be attributed to the microencapsulated formulations. The in vitro antitumor activity was assessed using HSC-3 (human oral squamous carcinoma; head and neck) and U-87 MG (human glioblastoma grade IV; astrocytoma) cancer cells. Cytotoxicity studies for both cell lines showed that the polymer coated, drug loaded MOFs exhibited better anticancer activity compared to free paclitaxel and cisplatin solutions at different concentrations., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and terminal alkynes (CuAAC), better known as "click" reaction, has triggered the use of 1,2,3-triazoles in bioconjugation, drug discovery, materials science and combinatorial chemistry. Here we report a new series of water-soluble catalysts based on N-heterocyclic carbene (NHC)-Cu complexes which are additionally functionalized with a sulfonate group. The complexes show superior activity towards CuAAC reactions and display a high versatility, enabling the production of triazoles with different substitution patterns. Additionally, successful application of these complexes in bioconjugation using unprotected peptides acting as DNA binding domains was achieved for the first time. Mechanistic insight into the reaction mechanism is obtained by means of state-of-the-art first principles calculations.

To optimally design next generation catalysts a thorough understanding of the chemical phenomena at the molecular scale is a prerequisite. Apart from qualitative knowledge on the reaction mechanism, it is also essential to be able to predict accurate rate constants. Molecular modeling has become a ubiquitous tool within the field of heterogeneous catalysis. Herein, we review current computational procedures to determine chemical kinetics from first principles, thus by using no experimental input and by modeling the catalyst and reacting species at the molecular level. Therefore, we use the methanol-to-olefin (MTO) process as a case study to illustrate the various theoretical concepts. This process is a showcase example where rational design of the catalyst was for a long time performed on the basis of trial and error, due to insufficient knowledge of the mechanism. For theoreticians the MTO process is particularly challenging as the catalyst has an inherent supramolecular nature, for which not only the Brønsted acidic site is important but also organic species, trapped in the zeolite pores, must be essentially present during active catalyst operation. All these aspects give rise to specific challenges for theoretical modeling. It is shown that present computational techniques have matured to a level where accurate enthalpy barriers and rate constants can be predicted for reactions occurring at a single active site. The comparison with experimental data such as apparent kinetic data for well-defined elementary reactions has become feasible as current computational techniques also allow predicting adsorption enthalpies with reasonable accuracy. Real catalysts are truly heterogeneous in a space- and time-like manner. Future theory developments should focus on extending our view towards phenomena occurring at longer length and time scales and integrating information from various scales towards a unified understanding of the catalyst. Within this respect molecular dynamics methods complemented with additional techniques to simulate rare events are now gradually making their entrance within zeolite catalysis. Recent applications have already given a flavor of the benefit of such techniques to simulate chemical reactions in complex molecular environments.

The catalytic activity of the zirconium terephthalate UiO-66(Zr) can be drastically increased by using a modulation approach. The combined use of trifluoroacetic acid and HCl during the synthesis results in a highly crystalline material, with partial substitution of terephthalates by trifluoroacetate. Thermal activation of the material leads not only to dehydroxylation of the hexanuclear Zr cluster but also to post-synthetic removal of the trifluoroacetate groups, resulting in a more open framework with a large number of open sites. Consequently, the material is a highly active catalyst for several Lewis acid catalyzed reactions.

A vanadium based metal-organic framework (MOF), VO(BPDC) (BPDC(2-) = biphenyl-4,4'-dicarboxylate), adopting an expanded MIL-47 structure type, has been synthesized via solvothermal and microwave methods. Its structural and gas/vapor sorption properties have been studied. This compound displays a distinct breathing effect toward certain adsorptives at workable temperatures. The sorption isotherms of CO(2) and CH(4) indicate a different sorption behavior at specific temperatures. In situ synchrotron X-ray powder diffraction measurements and molecular simulations have been utilized to characterize the structural transition. The experimental measurements clearly suggest the existence of both narrow pore and large pore forms. A free energy profile along the pore angle was computationally determined for the empty host framework. Apart from a regular large pore and a regular narrow pore form, an overstretched narrow pore form has also been found. Additionally, a variety of spectroscopic techniques combined with N(2) adsorption/desorption isotherms measured at 77 K demonstrate that the existence of the mixed oxidation states V(III)/V(IV) in the titled MOF structure compared to pure V(IV) increases the difficulty in triggering the flexibility of the framework.