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Magnetic sustentation experiments are employed to monitor the adsorption process of a supramolecularly assembled MOF in solution.

The sol–gel method provides a simple and versatile synthesis route to prepare low temperature curable metal-organic coatings photocatalytically active by visible light.

The synergistic combination of a zirconium metal–organic cluster and a Keggin type polyoxotungstate led to a chemically stable and photoactive porous material.

Herein we explore the opportunities arising from combining bicyclic amine cations with halometallate anions to build organic–inorganic hybrid materials. We will use the crystal engineering approach in these materials, focusing on the tuning of the organic cation, which is mainly responsible for obtaining both new plastic states at high temperature and electrical behaviour below the plastic temperature. Precisely, this work explores the influence of the ketonization of the bicyclic quinuclidine molecule (C7H13N)+, which, combined with the tetrachloroferrate(1-) anion, gives the compound (3-oxoquinuclidinium)[FeCl4]. Interestingly, crystallization in the presence of humidity is enough to obtain an isostructural hydrate phase of formula (3-oxoquinuclidinium)[FeCl4]·H2O. Although the organic–inorganic layered structure is the same in both compounds, the three-dimensional magnetic ordering disappears after the intercalation of crystallization water molecules. A heat treatment above 400 K allows the removal of water obtaining the non-hydrate phase. Finally, the temperature evolution of the electric and magnetic behaviour will be compared with other previously reported hybrid organic–inorganic materials built with tetrachloroferrate ions and quinuclidinium-based cations. Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P, MAT2017-83631-C3-3-R and MAT2017-86453-R) is acknowledged. The authors gratefully acknowledge technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). The paper is (partly) based on the results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona and Institute Laue-Langevin (ILL) in Grenoble (Proposals 5-31-2673 and 5-12-358).

Metal-organic frameworks (MOFs) imply an appealing source of photocatalysts as they combine porosity with tailorable electronic properties and surface chemistry. Herein, we report a series of unprecedented metal-organic aerogels (MOAs) comprised by Ti(IV) oxo-clusters and aromatic dicarboxylic linkers as an alternative to microporous MIL-125 and MIL-125-NH2 MOFs. Discrete titanium oxo-clusters polymerized upon the addition of the dicarboxylic linkers to give rise to a metal-organic gel. Their supercritical drying led to aerogels comprised by nanoscopic particles (ca. 5-10 nm) cross-linked into a meso/macroporous microstructure with surface area ranging from 453 to 617 m2 center dot g-1, which are comparatively lower than the surface area of the microporous counterparts (1336 and 1145 m2 center dot g-1, respectively). However, the meso/macroporous microstructure of MOAs can provide a more fluent diffusion of reagents and products than the intrinsic porosity of MOFs, whose narrower channels are expected to imply a more sluggish mass transport. In fact, the assessment of the continuous visible-light-driven photocatalytic CO2 reduction into methanol shows that MOAs (221-786 mmol center dot g-1 center dot h-1) far exceed not only the performance of their microporous counterparts (49-65 mmol center dot g-1 center dot h-1) but also surpass the production rates provided by up-to-date reported photocatalysts. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Oscar Castillo and Jonathan Albo report financial support was provided by Basque Government. Oscar Castillo and Estibaliz Aranzabe report financial support was provided by Spanish Ministry of Science and Innovation. Estibaliz Aranzabe reports financial support was provided by European Union. The authors gratefully acknowledge the financial support from the European Union's Horizon 2020 research and innovation program (grant agreement No.101037428), the Basque Government (KK-2016/00095-LISOL IT1291-19 and IT1722-22) and the Spanish Ministry of Science and Innovation (TED2021-129810B-C21 and TED2021-129810B-C22 funded by MCIN/AEI/10.13039/501100011033 and Next Generation EU/PRTR, PID2019-108028GB-C21 and PID2019-104050RA-I00 funded by MCIN/AEI/10.13039/501100011033). Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, and ESF) is also acknowledged.

UiO-66, reported in 2008, inspired the ongoing chemistry of group 4 metal-organic frameworks and it is still one of the most studied MOFs due to its exceptional stability. The tightness of their building blocks and bond strength make it tough to access new topologies, unless the building blocks are changed or defect engineering is employed, which in turn lead to different nominal stoichiometries. However, well selected structure directing agents and harsh synthesis conditions allowed the isolation of the first polymorph of UiO-66, named EHU-30. Herein, we provide evidence for the generalization of the synthetic approach with four new EHU-30 isoreticular compounds, based on amino-functionalized linkers and zirconium and hafnium as metal centres: EHU-30-NH2(M) and EHU-30-NHR(M) (M: Zr, Hf; R: 2-carboxypropyl). The crystal structure analysis reveals that their framework is more porous than that of their polymorphic counterpart. Furthermore, due to the current relevance of MOFs in greenhouse gas capture and in water harvesting methodologies, we have explored CO2 and water vapour adsorption on the new polymorphic phases, by means of experimental and computational resources, and compared to the parent EHU-30. The amino functionalization makes the EHU-30 series more prone to CO2 and water vapour adsorption. Besides, the water adsorption isotherms show an interesting crossing sensitive to temperature, sorption cycles and functionalization of the linker, which has been attributed to a localized structural transformation from EHU-30 to UiO-66. Finally, time-of-flight (TOF) powder neutron diffraction experiments were also conducted to locate the preferred adsorption sites for water in functionalized and parent EHU-30 structures.

The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (, This work has been supported by the Spanish MINECO (PID2019-106268GB-C32, MAT2016-77608-C3-1-P, PCI2018-093081, PID2019-108028GB-C21, and RTI2018-095622-B-I00), the Catalan AGAUR (project 2017 SGR 238), Basque Government (IT1291-19), and through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M). It was also funded by the CERCA Program/Generalitat de Catalunya. ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (Grant No. SEV-2017-0706).

Herein, we describe and study a new family of isostructural multifunctional metal-organic frameworks (MOFs) with the formula {[Ln

Clustering chemistry is a key point in the design and synthesis of the secondary building units that comprise metal-organic frameworks (MOFs) based on group IV metals. In this work, the first stages of the zirconium-carboxylate clustering process in alcohol/water mixtures are studied in detail using the monocarboxylic benzoic and hydroxybenzoic acids to avoid the polymerization. Mass spectroscopy measurements performed on the reactions revealed the presence of hexa- and pentanuclear species even at low pH values and also evidenced the acid-base nature and pH dependence of the transformation between both species. The control on the chemistry governing the equilibria between these species has allowed us to isolate six new compounds in the solid state. The single-crystal X-ray diffraction analysis revealed that they are closely related to the well-known [Zr

ACKNOWLEDGMENTS The authors thank SGIker of UPV/EHU and European funding (ERDF and ESF) for technical and human support as well as wish to acknowledge the terrific help of all reviewers of the present manuscript whose comments helped to improve the quality of the work., Supporting Information The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00544., Funding E.E. is grateful to the Government of the Basque Country for the predoctoral fellowship and R.F.M. to the Junior Research Position CEECIND/ 00553/2017. The research contract of FF (REF-168-89-ARH/2018) is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in nos. 4, 5, and 6 of article 23 of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 July. This work was developed within the scope of the projects given by the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21), Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19), Junta de Andalucía (FQM-394), University of the Basque Country (GIU 20/028), and CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020)., Herein, we describe and study a new family of isostructural multifunctional metal–organic frameworks (MOFs) with the formula {[Ln5L6(OH)3(DMF)3]·5H2O}n (where (H2L) is 3-amino-4-hydroxybenzoic acid ligand) for magnetism and photoluminescence. Interestingly, three of the materials (Dy-, Er-, and Yb-based MOFs) present single-molecule magnet (SMM) behavior derived from the magnetic anisotropy of the lanthanide ions as a consequence of the adequate electronic distribution of the coordination environment. Additionally, photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu–Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO2 sorption capacity., Government of the Basque Country, Junior Research Position CEECIND/ 00553/2017, National funds (OE), Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21), Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19), Junta de Andalucía (FQM-394), University of the Basque Country (GIU 20/028), CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020)

Scientific reports 12(1), 8505 (2022). doi:10.1038/s41598-022-11846-w, The doping of zirconium based EHU-30 and EHU-30-NH$_2$ metal–organic frameworks with copper(II) yielded a homogeneous distribution of the dopant with a copper/zirconium ratio of 0.04–0.05. The doping mechanism is analysed by chemical analysis, microstructural analysis and pair distribution function (PDF) analysis of synchrotron total scattering data in order to get deeper insight into the local structure. According to these data, the Cu(II) atoms are assembled within the secondary building unit by a transmetalation reaction, contrarily to UiO-66 series in which the post-synthetic metalation of the MOF takes place through chemical anchorage. The resulting materials doubled the overall performance of the parent compounds for the CO$_2$ electroreduction, while retained stable the performance during continuous transformation reaction., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Correction for ‘An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters’ by Jon Pascual-Colino et al., Inorg. Chem. Front., 2023, https://doi.org/10.1039/d2qi01994a.

The temperature evolution of the physical properties of the (quinuclidinium)[FeCl4] compound shows an unprecedented series of phase, structural and magnetic transitions. Above 390 K, a plastic phase (also termed as “rotator phases”) is observed (phase I). Between 390 K and 280 K, an intermediate phase solved in a non-centrosymmetric space group has been characterized. Crystallographic studies show that the compound crystallizes in the Pbc21 polar space group (phase II), and therefore the phase transition between I and II involves a paraelectric-to-polar phase transition. This result is confirmed by complex dielectric permittivity. Moreover, the real part of the dielectric permittivity shows a giant increase above 390 K, reaching a maximum value of 105 that is notably larger than any other hybrid compound previously reported. Below 280 K, a third structural phase transition is observed, which involves the doubling of the unit cell and a change of symmetry due to the blocking of counter-ions, phase III crystallizing in the Pbca centrosymmetric space group. Below 3.5 K, long-range magnetic order is detected. Neutron diffraction below this order temperature suggests breaking of symmetry and the magnetic structure in phase IV was solved in the P21′21′21 Shubnikov space group, giving rise to a ferrimagnetic structure that allows a net ferromagnetic signal along the c-axis.

The direct reaction between Cu(CH3COO)2 and uracil-1-acetic acid in water gives rise to the formation of a hydrogel consisting of entangled nanometric ribbons of a crystalline antiferromagnetic 1D Cu(ii) coordination polymer (CP) decorated with biocompatible uracil nucleobases. This hydrogel is the precursor for the preparation of a meso/macroporous ultralight aerogel that shows a remarkable Young's modulus. As a proof-of-concept of the molecular recognition capability of the terminal uracil moieties anchored at Cu(ii) CP chains, this material has been tested as the selective stationary phase for the separation of nucleobase derivatives in HPLC columns.

This work assesses the performance of Cu(II) and Bi(III)-based metal-organic framework (HKUST-1 and CAU-17, respectively) blends into the electroreduction of CO2 to alcohols in a filter-press electrochemical cell. The bimetallic materials are supported onto porous carbon paper to form gas diffusion electrodes with a favorable continuous electrochemical conversion of CO2 to methanol and ethanol, together with formic acid and gas-phase products (i.e. hydrogen, carbon monoxide and ethylene) in a 0.5 M KHCO3 aqueous solution. The maximum reaction rates and faradaic efficiencies for CO2 conversion to methanol and ethanol are rCH3OH=29.7 μmol·m−2·s-1 (FE = 8.6%) and rC2H5OH=48.8 μmol·m−2·s-1 (FE = 28.3%), respectively, at j = 20 mA·cm−2 which enhanced the values obtained at homometallic Cu and Bi-based materials independently. This denotes a synergic effect of Cu and Bi-based MOFs, associated with a favored interplay between the actives sites and reaction intermediates, prompting methanol formation and C C coupling reaction to ethanol. The results also show that reaction selectivity to produce alcohols can be controlled by Cu/Bi loading in the electrode surface and current density applied to the system. A 12% bismuth content seems to be the optimum for the production of alcohols (FEalcohols = 36.9%, Salcohols = 0.32). Regarding the current density, CO2 reduction is more selective to methanol with a j=10 mA·cm−2 (FECH3OH = 18.2%), while at j = 20 mA·cm−2, ethanol becomes the dominant CO2 reduction alcohol (FEC2H5OH = 28.3%). The performance of the Cu/Bi-MOFs remains also pseudo-stable after 5 h of operation denoting the potential of the mixed metal-organic systems for the utilization of CO2.

Reactions of N-methylated adenine (9-methyladenine and 3-methyladenine) with water-soluble oxalato complexes in the presence of potassium oxalate yields a series of oxalato-bridged complexes with the nucleobases as pendant ligands whose crystal structures and magnetic properties are reported herein. The complexes [M2(µ-ox)2(9Meade)3]n [M(II) = Zn (1), Cu (2); where ox = oxalato and 9Meade = 9-methyladenine] are composed of infinite corrugated one-dimensional chains in which two types of metal(II) centres are sequentially bridged by asymmetric bis-bidentate oxalato ligands and their coordination polyhedra are filled by N7-coordinated 9-methyladenine molecules giving rise to two different chromophores: an octahedral N2O4 donor set with the nucleobase moieties in trans-arrangement, and square based pyramidal NO4 coordination polyhedra. The cohesiveness of their supramolecular 3D architectures is achieved by means of an extensive network of non-covalent interactions including a short contact between the minor groove N3 site of the model 9-methyladenine and the oxalato bridging ligand from a neighbouring chain. This unconventional interaction between the lone pair of the pyrimidinic nitrogen atom of the nucleobase and the π-system of the oxalate anion has been analysed and discussed in the light of available structural data for analogous systems. The compounds {[M(µ-ox)(H2O)(3Meade)]·H2O}n [M(II) = Zn (3), Co (4) and Mn (5); where 3Meade = 3-methyladenine], and {[Cu(µ-ox)(3Meade)2]·4H2O}n (6) are comprised of zig–zag metal-oxalato chains, with the oxalato adopting a symmetric bis-bidentate coordination mode. The octahedral environment of the metals is completed in a cis-arrangement by one water molecule and the imidazole N7 donor site of a 3-methyladenine ligand for 3–5, and by two N7-coordinated nucleobases for 6. The crystal packing of the chains leads to the presence of channels with dimensions of 5 × 10 A for 6, and 4 × 6 A for 3–5 which are occupied by crystallization water molecules. The non-covalent interactions of the nucleobases among them and with the metal-oxalato framework have been studied in detail as well as the magnetic interactions mediated by the bridging oxalato ligand.

The slot-die process is an appealing technology for the fabrication of coatings on large-area substrates. However, its application on the production of photocatalytic coatings based on sol–gel formulations remains virtually unexplored. Thus, assessing the suitable formulation of the sol and operational parameters that allow one to yield high-efficacy photocatalyst coatings is a current challenge. This work aims to analyze the transferability of titania sol formulation optimized for dip-coating processes to slot-die technology. In this sense, firstly, the sol formulation is optimized by analyzing the influence of several types of surfactants on the microstructural features and photoactivity of TiO2 coatings’ growth on glass substrates. All formulations rendered a meaningful porosity and nanoscopic anatase crystallites (11–15 nm) with optical band gap values close to the expectation (3.25–3.31 eV). Accordingly, the performance of the photocatalytic dye degradation was closely related to the porosity and crystallite size led by each titania sol, and no meaningful differences were found between the results provided by the coatings developed by dip-coating and the slot-die method, which demonstrates the capability of the latter for its application on a large-scale fabrication of photocatalytic coatings. This research was funded by the Basque Government (IT1291-19), the Spanish Ministry of Science and Innovation (MICINN project: PID2019-108028GB-C21), and the European Union’s Horizon 2020 research and innovation program (grant agreement N° 792103 SOLWARIS).

Summary Using a photocatalytic window can simplify the design of an optofluidic microreactor, providing also a more straightforward operation. Therefore, the development of TiO2 coatings on glass substrates seems appealing, although a priori they would imply a reduced accessible area compared with supported nanoparticle systems. Considering this potential drawback, we have developed an endurable photocatalytic window consisting on an inner protective SiO2 layer and an outer mesoporous anatase layer with enhanced surface area and nanoscopic crystallite size (9–16 nm) supported on a glass substrate. The designed photocatalytic windows are active in the CO2-to-methanol photocatalytic transformation, with maximum methanol yield (0.52 μmol·h−1·cm−2) for greatest porosity values and minimum crystallite size. Compared with benchmark supported nanoparticle systems, the nanoscopic thickness of the coatings allowed to save photoactive material using only 11–22 μg·cm−2, while its robustness prevented the leaching of active material, thus avoiding the decay of performance at long working periods., Graphical abstract, Highlights • Photocatalytic windows provide enhanced operation of optofluidic microreactors • Use of TiO2 nanometric coatings reduces the required photocatalyst amount • The robustness of the coating implies stability upon long-working periods • CO2-to-CH3OH conversion performance is related to the porosity and crystallite size, Chemistry; Catalysis; Engineering

Quinuclidinium salts and their derivatives are now in the focus of materials science as building units of multifunctional materials. Their properties can be easily switchable, allowing their use in a wide range of physical applications. One type of these kinds of materials, the homochiral hybrid halometallate ferroelectric compounds, is not well understood. In this work, (R)-( )-3-quinuclidinol hydrochloride was used in the synthesis of ((R)-( )-3-hydroxyquinuclidium)[FeCl4]. The use of this enantiomeric cation forces crystallographic non-centrosymmetry, which was confirmed by polarimetry and circular dichroism spectroscopy. We studied the physical properties of this compound at different temperatures by single crystal, synchrotron and neutron powder X-ray diffraction, which showed a rich series of structural and magnetic phase transitions. From synchrotron powder X-ray diffraction data, a plastic phase was observed above 370 K (phase I). Between 370 K and ca. 310 K, an intermediate polar phase was detected, solved in a non-centrosymmetric polar space group (C2) (phase II). Below ca. 310 K, the compound crystallizes in the triclinic P1 non-centrosymmetric space group (phase III) which is maintained down to 4 K, followed by phase IV, which shows tridimensional magnetic ordering. The temperature evolution of the neutron diffraction data shows the appearance of new reflections below 4 K. These reflections can be indexed to a commensurate propagation vector k = (0, 0, 12). The magnetic structure below TN was solved in the Ps1 Shubnikov space group, which gives rise to an antiferromagnetic structure, compatible with the magnetometry measurements. Near room temperature, the crystal phase transition is associated with a dielectric change. In particular, the phase transition between phase III (S.G.:P1) and phase II (S.G.:C2) involves an increase of symmetry between two non-centrosymmetric space groups. Therefore, it allows, by symmetry, the emergence of ferroelectric and ferroelastic ordering. Piezoresponse force microscopy (PFM) imaging measurements provided evidence for polarization switching and a local ferroelectric behavior of phase III at room temperature. Additionally, the obtained butterfly curve and hysteresis loop by PFM exhibits a low coercive voltage of B10 V. This value is remarkable, since it approaches those obtained for materials with application in ferroelectric random access memories (FeRAMs). Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P, MAT2017-83631-C3-3-R, MAT2017-86453-R, PGC2018-097520-A-100 and PID2019-104050RAI00) is acknowledged. The authors gratefully acknowledge the technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). Carmen Martín is grateful to VI PPIT-2018 from Universidad de Sevilla. The paper is (partly) based on the results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona (proposal 2019083666) and Institute Laue-Langevin (ILL) of Grenoble (Proposals 5-31-2580 and 5-31-2460).

Capture and sensing of emerging pollutants is one of the increasing environmental concerns due to the adverse ecological and human health effects. Here, we report the synthesis of a supramolecular metal-organic framework (SMOF) [CrCu6(m-H2O)6(m3-OH)6(m-adeninato-kN33:kN9)6](SO4)1.5 which is able to capture anionic drugs and exhibits magnetic properties useful for sensing purposes. The features of the nucleobase decorated CrCu6 building block allow the incorporation of up to 9 drug molecules (i.e., ibuprofen and naproxen in this work) per heptameric entity. In addition, we provide a simple way to quantify the incorporated number of drug molecules through a magnetic sustentation experiment in which the field required to keep the particles attached to the electromagnet pole is linearly related to the total mass of the anionic counterion. In this way, it also provides an easy way to determine the amount of entrapped drug molecules, making this SMOF a promising candidate for environmental remediation technologies. This work has been funded by the Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50), the Gobierno Vasco/Eusko Jaurlaritza (PIBA18/14; IT1291-19), the Ministerio de Economía y Competitividad (MAT2016-75883-C2-1-P), the Ministerio de Ciencia e Innovación (PID2019-108028GB-C21), and FEDER funds. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, and ESF) is also acknowledged.

The hybrid compound [Cu(cyclam)(H2O)2]0.5[{Cu(cyclam)}1.5{B-H2As2Mo6O26(H2O)}]·9H2O (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane) was synthesized in aqueous solution by reacting the {Cu(cyclam)}2+ complex with a mixture of heptamolybdate and an arsenate(V) source. Crystal packing of 1 exhibits a supramolecular open-framework built of discrete covalent molybdoarsenate/metalorganic units and additional [Cu(cyclam)(H2O)2]2+ cations, the stacking of which generates squarelike channels parallel to the z axis with an approximate cross section of 10 × 11 Å2 where all the hydration water molecules are hosted. Thermal evacuation of solvent molecules yields a new anhydrous crystalline phase, but compound 1 does not preserve its single-crystalline nature upon heating. However, when crystals are dehydrated under vacuum, they undergo a structural transformation that proceeds via a single-crystal-to-single-crystal pathway, leading to the anhydrous phase [{Cu(cyclam)}2(A-H2As2Mo6O26)] (2). Total dehydration results in important modifications within the inorganic cluster skeleton which reveals an unprecedented solid-state B to A isomerization of the polyoxoanion. This transition also involves changes in the CuII bonding scheme that lead to covalent cluster/metalorganic layers by retaining the open-framework nature of 1. Compound 2 adsorbs ambient moisture upon air exposure, but it does not revert back to 1, and the hydrated phase [{Cu(cyclam)}2(A-H2As2Mo6O26)]·6H2O (2h) is obtained instead. Structural variations between 1 and 2 are reflected in electron paramagnetic resonance spectroscopy measurements, and the permanent microporosity of 2 provides interesting functionalities to the system such as the selective adsorption of gaseous CO2 over N2., A supramolecular open framework built of copper(II)-complexes of a macrocyclic tetraaza ligand and arsenomolybdate anions undergoes a single-crystal-to-single-crystal transformation upon dehydration that implies an unprecedented solid state cluster isomerization. The permanent porosity of the system allows the selective adsorption of CO2 over N2.

The catalytic activity of two halometallate complexes based on imidazolium cations, (dimim)[FeCl4] (1) and (dimim)2[Fe2Cl6(μ-O)] (2), was evaluated in the glycolysis of polyethylene terephthalate (PET), either under conventional heating or microwave-assisted conditions. The two procedures led to the formation of bis(2-hydroxyethyl)terephthalate (BHET) as the major product with high yields, also allowing the isolation and structural characterization of a new polymorph. The influence of the halometallate structure on the catalytic activity was investigated, and additional experimental studies proved the involvement of both the imidazolium cation and metal anion in the reaction mechanism. The comparison of both approaches showed the advantages of the microwave methodology in terms of efficiency and time saving. Indeed, the use of ground PET and microwave heating provided quantitative yields of BHET. Under conventional heating conditions, the dinuclear iron complex gave a slightly lower yield than (dimim)[FeCl4] (74% vs. 77% for post-consumer PET) after 24 h of reaction. However, the microwave-assisted process led to comparable results in remarkably shorter reaction times (2 h). Interestingly, complex 2, containing the dipolar [Fe2Cl6(μ-O)]2− moiety, provided higher yields than 1 with the non-dipolar [FeCl4]− anion (77% vs. 69%). This behaviour has been rationalized on the basis of dielectric heating mechanisms (polarization and conduction), and it suggests a new approach towards obtaining more efficient catalysts by tailoring the catalytic species to be active in both heating mechanisms. Financial support from the Spanish Ministerio de Ciencia e Innovación (Projects MAT2014-55049-C2-R and MAT2016-75883-C2-1-P), Universidad del País Vasco/EuskalHerrikoUnibertsitatea (GIU17/50 and PPG17/37). Universidad de Cantabria (Proyecto Puente convocatoria 2018 financed by SODERCAN-FEDER).

Six novel coordination polymers (CPs) based on alkaline-earth (AE) metal ions and two sorts of aminonicotinate ligands, namely [M(μ-2ani)(μ3-2ani)(μ-DMF)]n [MII = Sr (1) and Ba (2)], {[M(μ-6ani)2(H2O)2]·3H2O}n [MII = Ca (3) and Sr (4)], {[Ca(μ-6ani)2(H2O)2]}n (5) and {[Ba(6ani)2(H2O)3]·7H2O}n (6) [where 2ani = 2-aminonicotinate and 6ani = 6-aminonicotinate] have been synthesized and well characterized. All compounds are firstly built up with AE-carboxylate infinite rods that provide compact 2D-layered structures in 1 and 2 but open architectures containing microchannels in an AE-6ani system. Interestingly, the architecture of 3 behaves as a flexible platform which undergoes spontaneous dehydration to yield compound 5. Structural transition occurring from 3 to 5 has been supported by periodic density functional theory (DFT) calculations and X-ray diffraction data. In this regard, compound 6 contains a high amount of solvent molecules which suggests the existence of pores in its structure. A deep study of the optical properties including a detailed experimental characterization and DFT based computational calculations of these compounds supports a fascinating photoluminescence performance which entails a bright blue emission accompanied by persistent green afterglows at low temperature, especially for compound 5 as reflected by its lifetime (τ ≈ 1.4 s). In addition to its strong room temperature emission properties, we took advantage of the open yet stable structure of compound 4, to check its viability as a new material sensitive to the presence of solvents and/or transition metal ions, via significant quenching of the luminescence of 4. Remarkably, 4 is shown to be a particularly efficient sensor for some water soluble pollutants.

Since its discovery in 2008, the paradigmatic UiO-66 has behaved as the germ that has prompted the chemistry of group-4 metal based metal–organic frameworks, all of them featuring outstanding thermal and chemical stability. Herein we present the first polymorph of UiO-66 and the key conditions that led to its formation.

This work is aimed at the analysis of the interactions that drive the assembling of coordination metal-organic polymers based on biological molecules. Single-crystal X-ray diffraction data show that the compound 1D-{[Cu2(μ-ade)4(H2O)2]·2[Cu(theoph)2]·∼10H2O}n (1) contains neutral rhomboid shaped chains sustained by the tridentate μ3-κN3:κN7:κN9 coordination mode of the adenine nucleobase. These chains are formed by dimeric copper/adeninato (ade) cores doubly bridged by monomeric copper/theophyllinato (theoph) entities with the alkaloid acting as peripheral ligand. The lack of direct intermolecular nucleobase···nucleobase interactions, due to their disruption by the crystallization water molecules, does not provide a highly porous material, but the irregular shape of the polymeric chain hinders their packing and allows the presence of a moderate amount of voids (16% of the unit cell volume) in good accordance with its adsorption capacity of 0.38 mmol CO2/g at 273 K. Thermogravimetric and variable temperature X-ray diffraction analyses show that the compound retains its structure up to 110 °C whereas above this temperature the release of the coordination water molecules produces a significant loss of crystallinity. Magnetic measurements indicate an overall antiferromagnetic behavior with a J value of −267 cm−1 within the dimeric entity.

This work is aimed at the analysis of the π–π stacking interactions as the driving force to develop porous supramolecular metal–organic frameworks (SMOFs) as an alternative to more directional hydrogen bonding interactions. Four compounds based on the interaction between rigid copper/adenine entities and theobromine/caffeine molecules have been synthesized: [Cu7(μ-ade)6(μ3-OH)6(μ-H2O)6](theo)2·∼28H2O (1), [Cu2(μ-ade)4(H2O)2]·3Htheo·∼7H2O (2), [Cu2(μ-ade)4(H2O)2]·2Htheo·∼18H2O (3), and [Cu2(μ-ade)4(H2O)2]·(caf)·∼6H2O (4). The blue compound 1 is formed by wheel-shaped cationic heptameric units where the copper atoms are bridged by hydroxide anions, water molecules, and adeninato ligands with a μ-κN3:κN9 coordination mode. The assembly of the heptameric entities and the theobrominate anions takes place mainly through π–π stacking interactions involving the adeninato ligands and theobrominate moieties. Although compound 1 exhibits an open-framework with voids representing 37% of the unit cell, the plasticity ...

This contribution addresses standing questions about the nature and consequences of the ion self-assembly and magnetic structures, as well as the molecular motion of the crystalline structure as a function of the temperature, in halometalate materials based on imidazolium cation. We present the magnetic structure and magnetostructural correlations of 1-ethyl-2,3-dimethylimidazolium tetrachloridoferrate, (Edimim)[FeCl4], resolved by neutron diffraction studies. Single-crystal, synchrotron powder X-ray diffraction and powder neutron diffraction techniques have been combined to follow the temperature evolution on its crystallographic structure from 2 K close to its melting point (340 K). In this sense, slightly above room temperature (307 K) (Edimim)[FeCl4] presents a single-crystal to single-crystal transition (SCSC), from phase I (space group P21/n) to phase II (P21/m), accompanied by a notable increase in the disorder of the imidazolium cation, as well as in the metal complex anion. The temperature evolution and solid-phase transitions of the presented compound were followed in detail by synchrotron X-ray powder diffraction (SXPD), which confirms the occurrence of another phase transition at 330 K, phase III (P21/m), the crystal structure of which was elucidated from the SXPD pattern. Moreover, this material presents an anisotropic thermal expansion with a switch from axial positive to negative thermal expansion coefficients as the temperature is raised above the first phase transition, which has been correlated with the molecular motion of the imidazolium-based molecules, producing not only a shortening of the counterion···counterion distances but also the occurrence of different quasi-isoenergetic crystal structures as a function of the temperature.

Nucleobases are known as suitable builders of porous materials not only due to their high number of heteroatoms leading to different coordination modes, but also because they establish strong and predictable supramolecular interactions. In this contribution, nucleobases (adenine and guanine), functionalized nucleobases (9-methyladenine) and nucleobase derivatives (6-chloropurine) have been evaluated as ligands for the construction of metal–nucleobase building blocks which can afford supramolecular porous materials, analyzing in detail the requirements that these entities must fulfill and pointing out the relevance of accomplishing the suggested requisites. More concisely, we have evaluated a paddle-wheel shaped dimeric entity, [Cu2(μ-Hade)4Cl2]Cl2·8H2O (1) (where Hade: adenine), a trimeric unit, [Co3(μ-Hade)2(μ-Cl)4Cl2(H2O)4]·2H2O (2), a dimeric entity, [Cu2(Hgua)2(H2gua)2(μ-Cl)2Cl2(H2O)][CuCl4] (3) (where Hgua: guanine, H2gua: guaninium), a monomeric unit with 9-methyladenine as the pendant ligand, [Co(9-Meade)2(H2O)4]Cl2·2H2O (4), zigzag chains, [Cu2(μ-CH3COO)4(μ-9-Meade)]n·nCH3OH (5), and a monomeric unit with 6-chloropurinato ligands, [Co(6-Clpur)2(H2O)4]·4H2O (6).

The use of diazinedicarboxylate ligands in the construction of preconceived molecular entities and crystal structures deserves a good understanding of their coordination capacity in order to employ them for their rational design of functional materials. Therefore, the scope of the present review is to provide a comprehensive account of the architectures built up from these ligands rationalizing them through a conscientious analysis of their coordination modes in which the preponderance for establishing double chelating five-member rings holds a central role. The study covers the coordination features offered by transition, representative and lanthanide metal ions, with special emphasis on the coordination mode prevalence for each ligand. The structural rationalization is assessed during the examples along with their more relevant properties.

EnglishMetal-organic frameworks (MOFs) and supramolecular metal-organic frameworks (SMOFs) are porous crystalline materials which have become a very sub-stantial field of research over the last years. These materials consist of inorganic nodes (isolated metal atoms or metal clusters) which are linked by organic ligands (organic molecules). Nucleobases are suitable ligands since they provide porous metal-organic materials by means of coordination (MOF) or hydrogen-bonding interactions (SMOF). euskaraAzken urteotan konposatu metal-organiko porotsuek (MOFs, metal-or-ganic frameworks, eta SMOFs, supramolecular metal-organic frameworks ingelesez) hazkunde nabarmena izan dute. Konposatu horien egitura kristalinoak estekatzaile or-ganikoen (molekula organikoak) bidez lotutako nodo ez-organikoez (atomo edo kluster metalikoak) eraikita daude. Nukleobaseak gai dira estekatzaile organiko gisa aritu eta material metal-organiko porotsuak emateko, koordinazio- (MOF) zein hidrogeno-lotu-ren (SMOF) bitartez.

The hybrid compound [{Cu(cyclam)}3(W7O24)]·15.5H2O (1) (cyclam= 1,4,8,11-tetraaza-cyclotetradecane) was synthesized by reacting the {Cu(cyclam)}2+ complex with a tungstate source in water at pH = 8. Compound 1 exhibits an unprecedented three-dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF-like framework that displays water-filled channels. This dynamic architecture undergoes two sequential single-crystal-to-single-crystal transformations upon thermal evacuation of water molecules to result in the partially dehydrated [{Cu(cyclam)}3(W7O24)]·12H2O (2) and anhydrous [Cu(cyclam)]0.5[{Cu(cyclam)}2.5(W7O24)] (3) crystalline phases. These transitions are associated with cluster rotations and modifications in the CuII coordination geometries, which reduce the dimensionality of the original lattice to layered systems but preserving the porous nature. Phase 3 reverts to 2 upon exposure to ambient moisture, whereas the transition between 1 and 2 proved to be irreversible. The permanent microporosity of 3 was confirmed by gas sorption measurements (N2, CO2), which reveal a system of parallel channels made of wide cavities connected through narrow necks that limit the adsorption process, in good agreement with Grand Canonical Monte Carlo simulations.

Five new compounds of cytosine with first-row transition metals, (H2Cyt)2[CoCl4]·2(HCyt) (1), [CoBr2(HCyt)2] (2), [ZnCl2(HCyt)2] (3), [CuCl2(HCyt)2] (4), and [CuBr2(HCyt)2] (5) (in which HCyt = cytosine, H2Cyt = cytosinium cation), are reported. In 1, the protonation of one of the cytosine molecules facilitates base pairing with the neutral cytosine, instead of the expected coordination to the metal center. In all other compounds, neutral cytosine molecules are coordinated to the MII centers through N3 positions, forming monomeric entities. The supramolecular crystal structure of 1 is sustained by the base-pairing interactions between the 1H,3H-cytosinium cation and the neutral 1H-cytosine molecule through their Watson–Crick and sugar edges, giving rise to zig-zag supramolecular ribbons, in which neutral and cationic cytosine molecules alternate. In the isostructural compounds 2 and 3, only one of the cytosine molecules establishes base pairing through sugar-edge-forming supramolecular dimers, and the 3D cohesiveness is achieved by means of noncomplementary hydrogen bonding, involving the sugar edge of the other cytosine with the amino group and the bromide anions of the adjacent dimer. Compounds 4 and 5 show similar supramolecular arrangements, with cytosine molecules self-assembling along the sugar edge into 1D chains.

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl

A thorough characterization of the title compound, (dimim)2[Fe2Cl6(μ-O)], consisting of a (μ-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group P 1 ¯ (/α/β/γ)0 with modulation vector q = 0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (μ-oxido)-bridged binuclear iron(III) complex, as well as the molecular motion of the imidazolium cation within the crystalline structure as a response to the temperature effect. Finally, we present a deep magnetic study based on magnetic susceptibility, magnetization and Mössbauer measurements, where the strong antiferromagnetic exchange coupling detected is due to the occurrence of a μ-oxido bridge between the Fe(III), giving rise to an intra-dimeric antiferromagnetic exchange coupling of –308 cm−1.

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 10 6 S cm 1 at room temperature to 5.5 10 5 S cm 1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 financed by SODERCAN_FEDER), Universidad del Pa´ıs Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239- C2-(1,2)-P).