Enhanced CO2 Adsorption Affinity in a NbO‐type MOF Constructed from a Low‐Cost Diisophthalate Ligand with a Piperazine‐Ring Bridge

A metal–organic framework (NPC‐6) with an NbO topology based on a piperazine ring‐bridged diisophthalate ligand was synthesized and characterized. The incorporated piperazine group leads to an enhanced adsorption affinity for CO₂ in NPC‐6, in which the CO₂ uptake is 4.83 mmol g^?1 at 293 K and 1 bar, ranking among the top values of CO₂ uptake on MOF materials. At 0.15 bar and 293 K, the NPC‐6 adsorbs 1.07 mmol g^?1 of CO₂, which is about 55.1 % higher than that of the analogue MOF NOTT‐101 under the same conditions. The enhanced CO₂ uptake combined with comparable uptakes for CH₄ and N₂ leads to much higher selectivities for CO₂/CH₄ and CO₂/N₂ gas mixtures on NPC‐6 than on NOTT‐101. Furthermore, an N‐alkylation is used in the synthesis of the PDIA ligand, leading to a much lower cost compared with that in the synthesis of ligands in the NOTT series, as the former does not require a palladium‐based catalyst and borate esters. Thus, we conclude that NPC‐6 is a promising candidate for CO₂ capture applications.     

Analysis of High and Selective Uptake of CO2 in an Oxamide‐Containing {Cu2(OOCR)4}‐Based Metal–Organic Framework

The porous framework [Cu₂(H₂O)₂L] ? 4 H₂O ? 2 DMA (H₄L=oxalylbis(azanediyl)diisophthalic acid; DMA=N,N‐dimethylacetamide), denoted NOTT‐125, is formed by connection of {Cu₂(RCOO)₄} paddlewheels with the isophthalate linkers in L^4?. A single crystal structure determination reveals that NOTT‐125 crystallises in monoclinic unit cell with a=27.9161(6), b=18.6627(4) and c=32.3643(8) Å, β=112.655(3)°, space group P2₁/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three‐dimensional space. Cage A is constructed from twelve {Cu₂(OOCR)₄} paddlewheels and six linkers to form an ellipsoid‐shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across its central diameter. Cage B consists of six {Cu₂(OOCR)₄} units and twelve linkers and has a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT‐125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT‐125a, is responsible for excellent CO₂ uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO₂ over CH₄ or N₂. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO₂ and CH₄ with the linkers in NOTT‐125 reveals a set of strong interactions between CO₂ and the oxamide motif that are not possible with a single amide.     

Fine Tuning of MOF‐505 Analogues To Reduce Low‐Pressure Methane Uptake and Enhance Methane Working Capacity

We present a crystal engineering strategy to fine tune the pore chemistry and CH₄‐storage performance of a family of isomorphic MOFs based upon PCN‐14. These MOFs exhibit similar pore size, pore surface, and surface area (around 3000 m² g⁻¹) and were prepared with the goal to enhance CH₄ working capacity. [Cu₂(L2)(H₂O)₂]_n (NJU‐Bai 41: NJU‐Bai for Nanjing University Bai's group), [Cu₂(L3)(H₂O)₂]_n (NJU‐Bai 42), and [Cu₂(L4)(DMF)₂]_n (NJU‐Bai 43) were prepared and we observed that the CH₄ volumetric working capacity and volumetric uptake values are influenced by subtle changes in structure and chemistry. In particular, the CH₄ working capacity of NJU‐Bai 43 reaches 198 cm³ (STP: 273.15 K, 1 atm) cm⁻³ at 298 K and 65 bar, which is amongst the highest reported for MOFs under these conditions and is much higher than the corresponding value for PCN‐14 (157 cm³ (STP) cm⁻³).     

A Robust 3D Cage‐like Ultramicroporous Network Structure with High Gas‐Uptake Capacity

A three‐dimensional (3D) cage‐like organic network (3D‐CON) structure synthesized by the straightforward condensation of building blocks designed with gas adsorption properties is presented. The 3D‐CON can be prepared using an easy but powerful route, which is essential for commercial scale‐up. The resulting fused aromatic 3D‐CON exhibited a high Brunauer–Emmett–Teller (BET) specific surface area of up to 2247 m² g^?1. More importantly, the 3D‐CON displayed outstanding low pressure hydrogen (H₂, 2.64 wt %, 1.0 bar and 77 K), methane (CH₄, 2.4 wt %, 1.0 bar and 273 K), and carbon dioxide (CO₂, 26.7 wt %, 1.0 bar and 273 K) uptake with a high isosteric heat of adsorption (H₂, 8.10 kJ mol^?1; CH₄, 18.72 kJ mol^?1; CO₂, 31.87 kJ mol^?1). These values are among the best reported for organic networks with high thermal stability (ca. 600 °C).     

High capacity gas storage by a 4,8-connected metal-organic polyhedral framework

The polyhedral complex [Cu(4)L(H(2)O)(4)]solv (NOTT-140) shows a 4,8-connected structure of rare scu topology comprising octahedral and cuboctahedral cages; desolvated NOTT-140a shows a total CO(2) uptake of 314.6 cm(3) (STP) cm(-3) at 20 bar, 293 K, and a total H(2) uptake of 6.0 wt% at 20 bar, 77 K.     

Effect of Functionalized Groups on Gas‐Adsorption Properties: Syntheses of Functionalized Microporous Metal–Organic Frameworks and Their High Gas‐Storage Capacity

The microporous metal–organic framework (MMOF) Zn₄O(L1)₂ ? 9 DMF ? 9 H₂O ( 1‐H ) and its functionalized derivatives Zn₄O(L1‐CH₃)₂ ? 9 DMF ? 9 H₂O ( 2‐CH₃ ) and Zn₄O(L1‐Cl)₂ ? 9 DMF ? 9 H₂O ( 3‐Cl ) have been synthesized and characterized (H₃L1=4‐[N,N‐bis(4‐methylbenzoic acid)amino]benzoic acid, H₃L1‐CH₃=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐methylbenzoic acid, H₃L1‐Cl=4‐[N,N‐bis(4‐methylbenzoic acid)amino]‐2‐chlorobenzoic acid). Single‐crystal X‐ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three‐dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm² g^?1. Their pore volumes and surface areas decrease in the order 1‐H > 2‐CH₃ > 3‐Cl . Gas‐adsorption studies show that the H₂ uptakes of these samples are among the highest of the MMOFs (2.37 wt % for 3‐Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate–adsorbent interaction plays a more important role in the gas‐adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas‐adsorption properties at high pressure.     

A Robust Porous Metal–Organic Framework with a New Topology That Demonstrates Pronounced Porosity and High‐Efficiency Sorption/Selectivity Properties of Small Molecules

A robust porous metal–organic framework (MOF), [Co₃(ndc)(HCOO)₃(μ₃‐OH)(H₂O)]_n ( 1 ) (H₂ndc=5‐(4‐pyridyl)‐isophthalic acid), was synthesized with pronounced porosity. MOF 1 contained two different types of nanotubular channels, which exhibited a new topology with the Schlafli symbol of {4².6⁵.8³}{4².6}. MOF 1 showed high‐efficiency for the selective sorption of small molecules, including the energy‐correlated gases of H₂, CH₄, and CO₂, and environment‐correlated steams of alcohols, acetone, and pyridine. Gas‐sorption experiments indicated that MOF 1 exhibited not only a high CO₂‐uptake (25.1 wt % at 273 K/1 bar) but also the impressive selective sorption of CO₂ over N₂ and CH₄. High H₂‐uptake (2.04 wt % at 77 K/1 bar) was also observed. Moreover, systematic studies on the sorption of steams of organic molecules displayed excellent capacity for the sorption of the homologous series of alcohols (C₁–C₅), acetone, pyridine, as well as water.     

A Flexible Pro‐porous Coordination Polymer: Non‐conventional Synthesis and Separation Properties Towards CO2/CH4 Mixtures

The novel coordination polymers [Cu(Hoxonic)(H₂O)]_n ( 1 ) and [Cu(Hoxonic)(bpy)_0.5]_n ? 1.5 n H₂O ( 2?H₂O ) (H₃oxonic: 4,6‐dihydroxy‐1,3,5‐triazine‐2‐carboxylic acid; bpy: 4,4′‐bipyridine) have been isolated and structurally characterised by ab initio X‐ray powder diffraction. The dense phase 1 contains 1D zig‐zag chains in which Hoxonic dianions bridge square‐pyramidal copper(II) ions, apically coordinated by water molecules. On the contrary, 2?H₂O , prepared by solution and solventless methods, is based on 2D layers of octahedral copper(II) ions bridged by Hoxonic ligands, further pillared by bpy spacers. The resulting pro‐porous 3D network possesses small hydrated cavities. The reactivity, thermal, magnetic and adsorptive properties of these materials have been investigated. Notably, the adsorption studies on 2 show that this material possesses unusual adsorption behaviour. Indeed, guest uptake is facilitated by increasing the thermal energy of both the guest and the framework. Thus, neither N₂ at 77 K nor CO₂ at 195 K are incorporated, and CH₄ is only minimally adsorbed at 273 K and high pressures (0.5 mmol g^?1 at 2500 kPa). By contrast, CO₂ is readily incorporated at 273 K (up to 2.5 mmol g^?1 at 2500 kPa). The selectivity of 2 towards CO₂ over CH₄ has been investigated by means of variable‐temperature zero coverage adsorption experiments and measurement of breakthrough curves of CO₂/CH₄ mixtures. The results show the highly selective incorporation of CO₂ in 2 , which can be rationalised on the basis of the framework flexibility and polar nature of its voids.     

Microporous La–Metal–Organic Framework (MOF) with Large Surface Area

A microporous La–metal‐organic framework (MOF) has been synthesized by the reaction of La(NO₃)₃ ? 6 H₂O with a ligand 4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoate (TATAB) featuring three carboxylate groups. Crystal structure analysis confirms the formation of 3D MOF with hexagonal micropores, a Brunauer–Emmett—Teller (BET) surface area of 1074 m² g^?1 and high thermal and chemical stability. The CO₂ adsorption capacities are 76.8 cm³ g^?1 at 273 K and 34.6 cm³ g^?1 at 293 K, a highest measured CO₂ uptake for a Ln–MOFs.     

FeIII Quinolylsalicylaldimine Complexes: A Rare Mixed‐Spin‐State Complex and Abrupt Spin Crossover

A new synthesis of (8‐quinolyl)‐5‐methoxysalicylaldimine (Hqsal‐5‐OMe) is reported and its crystal structure is presented. Two Fe^III complexes, [Fe(qsal‐5‐OMe)₂]Cl ? solvent (solvent=2 MeOH ? 0.5 H₂O ( 1 ) and MeCN ? H₂O ( 2 )) have been prepared and their structural, electronic and magnetic properties studied. [Fe(qsal‐5‐OMe)₂] Cl ? 2 MeOH ? 0.5 H₂O ( 1 ) exhibits rare crystallographically independent high‐spin and low‐spin Fe^III centres at 150 K, whereas [Fe(qsal‐5‐OMe)₂]Cl ? MeCN ? H₂O ( 2 ) is low spin at 100 K. In both structures there are extensive π–π and C? H???π interactions. SQUID magnetometry of 2 reveals an unusual abrupt stepped‐spin crossover with T_1/2=245 K and 275 K for steps 1 and 2, respectively, with a slight hysteresis of 5 K in the first step and a plateau of 15 K between the steps. In contrast, 1 is found to undergo an abrupt half‐spin crossover also with a hysteresis of 10 K. The two compounds are the first Fe^III complexes of a substituted qsal ligand to exhibit abrupt spin crossover. These conclusions are supported by ⁵⁷Fe Mössbauer spectroscopy. Both complexes exhibit reversible reduction to Fe^II at ?0.18 V and irreversible oxidation of the coordinated qsal‐5‐OMe ligand at +1.10 V.     

A Versatile CuII Metal–Organic Framework Exhibiting High Gas Storage Capacity with Selectivity for CO2: Conversion of CO2 to Cyclic Carbonate and Other Catalytic Abilities

A linear tetracarboxylic acid ligand, H₄L, with a pendent amine moiety solvothermally forms two isostructural metal–organic frameworks (MOFs) L_M (M=Zn^II, Cu^II). Framework L_Cu can also be obtained from L_Zn by post‐ synthetic metathesis without losing crystallinity. Compared with L_Zn , the L_Cu framework exhibits high thermal stability and allows removal of guest solvent and metal‐bound water molecules to afford the highly porous, L_Cu′ . At 77 K, L_Cu′ absorbs 2.57 wt % of H₂ at 1 bar, which increases significantly to 4.67 wt % at 36 bar. The framework absorbs substantially high amounts of methane (238.38 cm³ g^?1, 17.03 wt %) at 303 K and 60 bar. The CH₄ absorption at 303 K gives a total volumetric capacity of 166 cm³ (STP) cm^?3 at 35 bar (223.25 cm³ g^?1, 15.95 wt %). Interestingly, the NH₂ groups in the linker, which decorate the channel surface, allow a remarkable 39.0 wt % of CO₂ to be absorbed at 1 bar and 273 K, which comes within the dominion of the most famous MOFs for CO₂ absorption. Also, L_Cu′ shows pronounced selectivity for CO₂ absorption over CH₄, N₂, and H₂ at 273 K. The absorbed CO₂ can be converted to value‐added cyclic carbonates under relatively mild reaction conditions (20 bar, 120 °C). Finally, L_Cu′ is found to be an excellent heterogeneous catalyst in regioselective 1,3‐dipolar cycloaddition reactions (“click” reactions) and provides an efficient, economic route for the one‐pot synthesis of structurally divergent propargylamines through three‐component coupling of alkynes, amines, and aldehydes.     

Different Spin‐State Behaviors in Isostructural Solvates of a Molecular Iron(II) Complex

The complex [FeL₂][BF₄]₂ ( 1 ; L=4‐(isopropylsulfanyl)‐2,6‐di(pyrazol‐1‐yl)pyridine) forms solvate crystals 1 ?solv (solv=MeNO₂, MeCN, EtCN, or Me₂CO). Most of these materials lose their solvent sluggishly on heating. However, heating 1 ?MeNO₂ at 450 K, or storing 1 ?EtCN under ambient conditions, leads to single‐crystal to single‐crystal exchange of the organic solvent for atmospheric moisture, forming 1 ?H₂O. Solvent‐free 1 ( 1 ?sf) can be generated in situ by annealing 1 ?H₂O at 370 K in the diffractometer or magnetometer. The different forms of 1 are isostructural (P2₁/c, Z=4) and most of them exhibit spin‐crossover (SCO) at 141≤T ≤212 K, depending on their solvent content. The exception is the EtCN solvate, whose pristine crystals remain high‐spin between 3–300 K. The cooperativity of the spin‐transitions depends on the solvent, ranging from gradual and incomplete when solv=acetone to abrupt with 17 K hysteresis when solv=MeCN. Our previously proposed relationship between molecular structure and SCO explains some of these observations, but there is no single structural feature that correlates with SCO in all the 1 ?solv materials. However, changes to the unit cell dimensions during SCO differ significantly between the solvates, and correlate with the SCO cooperativity. In particular, the percentage change in unit cell volume during SCO for the most cooperative material, 1 ?MeCN, is 10 times smaller than for the other 1 ?solv crystals.     

Isostructural Metal–Organic Frameworks Assembled from Functionalized Diisophthalate Ligands through a Ligand‐Truncation Strategy

Four isostructural metal–organic frameworks (MOFs) with various functionalized pore surfaces were synthesized from a series of diisophthalate ligands. These MOFs exhibit a new network topology of {4.6⁴.8}₂{4².6⁴}{6⁴.8²}₂{6⁶}. Hydrogen uptake as high as 2.67 wt % at 77 K/1 bar and CO₂ uptake of 15.4 wt % at 297 K/1 bar have been observed for PCN‐308, which contains ? CF₃ groups. The isostructural series of MOFs also showed reasonable adsorption selectivity of CO₂ over CH₄ and N₂.     

Mixed‐Ligand Zn‐MOFs for Highly Luminescent Sensing of Nitro Compounds

Three Zn^II metal‐organic frameworks (Zn‐MOFs), [Zn₂(tib)(HL¹)(H₂L¹)_0.5]?2H₂O ( 1 ), [Zn₂(tib)(L²)]?H₂O ( 2 ) and [Zn₃(tib)(L³)₂(H₂O)₆]?2 H₂O ( 3 ), have been prepared by reactions of 1,3,5‐tris(1‐imidazolyl)benzene (tib), and biphenyl‐3,3′,4,4′‐tetracarboxylic acid (H₄L¹), 4,4′‐oxydiphthalic acid (H₄L²), or benzene‐1,3,5‐tricarboxylic acid (H₃L³) with corresponding Zn^II salts, respectively. Single crystal structure analyses reveal that 1 and 2 are constructed by Zn‐centered polyhedra, tib and multidentate tetracarboxylate ligands to form 3‐dimensional frameworks. In contrast, when the tetracarboxylate ligands were replaced by tricarboxylate ligand, layered structure of 3 is produced. These compounds are further characterized by powder X‐ray diffraction, element analyses, thermogravimetric analyses and photoluminescent spectroscopy. The luminescent properties of three Zn‐MOFs dispersed in different solvents have been investigated systematically, demonstrating high sensitivity for the detection of nitro compounds via a fluorescence quenching mechanism.     

Lithium‐Functionalized Metal–Organic Frameworks that Show >10 wt % H2 Uptake at Ambient Temperature

We have used grand canonical Monte Carlo simulations with a first‐principles‐based force field to show that metal–organic frameworks (MOFs) with Li functional groups (i.e. C? Li bonds) allow for exceptional H₂ uptake at ambient temperature. For example, at 298 K and 100 bar, IRMOF‐1‐4Li shows a total H₂ uptake of 5.54 wt % and MOF‐200‐27Li exhibits a total H₂ uptake of 10.30 wt %, which are much higher than the corresponding values with pristine MOFs. Li‐functionalized MOF‐200 (MOF‐200‐27Li) shows 11.84 wt % H₂ binding at 243 K and 100 bar. These hydrogen‐storage capacities exceed the 2015 DOE target of 5.5 wt % H₂. Moreover, the incorporation of Li functional groups into MOFs provides more benefits, such as higher delivery amount, for H₂ uptake than previously reported Li‐doped MOFs.     

Local Coordination Geometry and Spin State in Novel FeII Complexes with 2,6‐Bis(pyrazol‐3‐yl)pyridine‐Type Ligands as Controlled by Packing Forces: Structural Correlations

A substituted 2,6‐bis(pyrazol‐3‐yl)pyridine (3‐bpp) ligand, H₄L, created to facilitate intermolecular interactions in the solid, has been used to obtain four novel Fe^II complexes: [Fe(H₄L)₂](ClO₄)₂ ? 2 CH₃NO₂ ? 2 H₂O, [Fe(H₄L)(H₂LBF₂)](BF₄) ? 5 C₃H₆O (H₂LBF₂ is an in situ modified version of H₄L), [Fe(H₄L)₂](ClO₄)₂ ? 2 C₃H₇OH and [Fe(H₄L)₂](ClO₄)₂ ? 4 C₂H₅OH. Changing of spin‐inactive components (solvents, anions or distant ligand substituents) causes differences to the coordination geometry of the metal that are key to the magnetic proper‐ ties. Magnetic measurements show that, contrary to the previously published complex [Fe(H₄L)₂](ClO₄)₂ ? H₂O ? 2 CH₃COCH₃, the newly synthesised compounds remain in the high‐spin (HS) state at all temperatures (5–300 K). A member of the known family of Fe^II/3‐bpp complexes, [Fe(3‐bpp)₂](ClO₄)₂ ? 1.75 CH₃COCH₃ ? 1.5 Et₂O, has also been prepared and characterised structurally. In the bulk, this compound exhibits a gradual and incomplete spin transition near 205 K. The single‐crystal structure is consistent with it being HS at 250 K and partially low spin at 90 K. Structural analysis of all these compounds reveals that the exact configuration of intermolecular interactions affects dramatically the local geometry at the metal, which ultimately has a strong influence on the magnetic properties. Along this line, the geometry of Fe^II in all published 3‐bpp compounds of known structure has been examined, both by calculating various distortion indices (Σ, Θ, θ and Φ) and by continuous shape measures (CShMs). The results reveal correlations between some of these parameters and indicate that the distortions from octahedral geometry observed on HS systems are mainly due to strains arising from intermolecular interactions. As previously suggested with other related compounds, we observe here that strongly HS‐distorted systems have a larger tendency to remain in that state.     

Construction of Two High‐Nuclear 3d‐4d Heterometallic Cluster Organic Frameworks by Introducing a Bifunctional Tripodal Alcohol as a Structure‐Directing Agent

Two unique heterometallic cluster organic frameworks, [Cd₄Mn^III₄Mn^II₆(Tri)₄(CH₃COO)₁₄(μ₄‐O)₂(μ₃‐O)₂(H₂O)₂] Cd(H₂O)₂?9 H₂O ( 1 ) and Cu[Cd₅Cu₆(Tri)₄(CH₃COO)₉(H₂O)₄]₂(CH₃COO)₃?24 H₂O ( 2 ) (H₃Tri=2‐(hydroxymethyl)‐2‐(pyridine‐4‐yl)‐1,3‐propanediol), have been successfully prepared by employing a bifunctional tripodal alcohol ligand as a structure‐directing agent. Crystal structure analyses reveal that 1 represents a rare example of frameworks constructed from Cd?Mn heterometallic chains, and 2 is the first heterometallic MOF based on highest‐nuclear Cd?Cu heterometallic cluster building blocks. Furthermore, the magnetic properties and gas adsorption abilities of 1 and 2 were systematically studied.     

Thermotropic Liquid Crystals Based on Extended 2,5‐Disubstituted‐1,3,4‐Oxadiazoles: Structure–Property Relationships,Variable‐Temperature Powder X‐ray Diffraction,and Small‐Angle X‐ray Scattering Studies

A class of extended 2,5‐disubstituted‐1,3,4‐oxadiazoles R¹‐C₆H₄‐{OC₂N₂}‐C₆H₄‐R² (R¹=R²=C₁₀H₂₁O 1 a , p‐C₁₀H₂₁O‐C₆H₄‐C?C 3 a , p‐CH₃O‐C₆H₄‐C?C 3 b ; R¹=C₁₀H₂₁O, R²=CH₃O 1 b , (CH₃)₂N 1 c ; F 1 d ; R¹=C₁₀H₂₁O‐C₆H₄‐C?C, R²=C₁₀H₂₁O 2 a , CH₃O 2 b , (CH₃)₂N 2 c , F 2 d ) were prepared, and their liquid‐crystalline properties were examined. In CH₂Cl₂ solution, these compounds displayed a room‐temperature emission with λ_max at 340–471 nm and quantum yields of 0.73–0.97. Compounds 1 d , 2 a – 2 d , and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized‐light optical microscopy and differential scanning calorimetry. Structure determination by a direct‐space approach using simulated annealing or parallel tempering of the powder X‐ray diffraction data revealed distinctive crystal‐packing arrangements for mesogenic molecules 2 b and 3 a , leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200–210 °C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable‐temperature X‐ray diffractometry. Nondestructive phase transitions (crystal‐to‐crystal, crystal‐to‐mesophase, mesophase‐to‐liquid) were observed in the diffractograms of 1 b, 1 d , 2 b, 2 d , and 3 a measured at 25–200 °C. Powder X‐ray diffraction and small‐angle X‐ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure–property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions.     

A Cationic MOF with High Uptake and Selectivity for CO2 due to Multiple CO2‐Philic Sites

The reaction of N‐rich pyrazinyl triazolyl carboxyl ligand 3‐(4‐carboxylbenzene)‐5‐(2‐pyrazinyl)‐1H‐1,2,4‐triazole (H₂cbptz) with MnCl₂ afforded 3D cationic metal–organic framework (MOF) [Mn₂(Hcbptz)₂(Cl)(H₂O)]Cl ? DMF ? 0.5 CH₃CN ( 1 ), which has an unusual (3,4)‐connected 3,4T1 topology and 1D channels composed of cavities. MOF 1 has a very polar framework that contains exposed metal sites, uncoordinated N atoms, narrow channels, and Cl^? basic sites, which lead to not only high CO₂ uptake, but also remarkably selective adsorption of CO₂ over N₂ and CH₄ at 298–333 K. The multiple CO₂‐philic sites were identified by grand canonical Monte Carlo simulations. Moreover, 1 shows excellent stability in natural air environment. These advantages make 1 a very promising candidate in post‐combustion CO₂ capture, natural‐gas upgrading, and landfill gas‐purification processes.     

Linear {NiII–LnIII–NiII} Complexes Containing Twisted Planar Ni(μ‐phenolate)2Ln Fragments: Synthesis,Structure, and Magnetothermal Properties

Sequential reaction of a multisite LH₄ ligand {2‐[2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino]‐2‐methylpropane‐1,3‐diol} with appropriate lanthanide salts followed by the addition of Ni(NO₃)₂ ? 6 H₂O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni₂Gd(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 1 ), [Ni₂Tb(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? CH₃CN ( 2 ), [Ni₂Dy(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 3 ), and [Ni₂Ho(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 4 ). Complexes 1 – 4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out‐of‐phase signal, χ′′_M , under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect.