Zn Metal Center Research Articles

Hydroxyacetone derived N4-methyl substituted thiosemicarbazone: Syntheses, crystal structures and spectroscopic characterization of later first-row transition metal complexes

The present work reports the syntheses, crystal structures and spectroscopic characterization of later first-row transition metal complexes of hydroxyacetone derived N4-methyl substituted thiosemicarbazone. The molecular structures of Co(II) and Ni(II) complexes are determined by single crystal X-ray diffraction method. The crystal structures reveal that the Co(II) and Ni(II) complexes have crystallized in monoclinic and triclinic crystal systems with C2/c and P-1 space groups, respectively. The ligand, 1-(1-hydroxypropan-2-ylidene)-N4-methylthiosemicarbazone ligates in a neutral, SNO tridentate fashion to the central metal ions. The numerous physicochemical investigations carried out to the synthesized complexes disclose the metal to ligand stoichiometry to be 1:2 in Co(II), Ni(II) and Zn(II) complexes whereas 1:1 in Cu(II) complex. The ligand environment forms a distorted octahedral geometry around Co(II), Ni(II) and Zn(II) metal centers, while square pyramidal geometry over Cu(II) ion. The in vitro antitubercular results against Mycobacterium tuberculosis affirm that the synthesized compounds are four-fold more active than the standard drug, Streptomycin and two-fold more active than the other two standards used, Pyrazinamide and Ciprofloxacin.

Impact of metal ions and organic ligands on uranium removal properties by zeolitic imidazolate framework materials

Highly porous zeolitic imidazolate frameworks (ZIFs), with disparate metal ions (ZIF-8 and ZIF-67), disparate organic ligands (ZIF-9 and ZIF-67), single or double central metal atoms (ZIF-8, Zn/Co-ZIF and ZIF-67) were prepared and used in the elimination of typical radionuclide U(VI). The detailed interaction mechanisms were studied by batch experiments, spectral analyses and DFT calculation. Langmuir isotherms model revealed a decreasing tendency to remove U(VI): ZIF-8 (540.4 mg/g) > Zn/Co-ZIF (527.5 mg/g) > ZIF-9 (448.6 mg/g) > ZIF-67 (368.2 mg/g). Based on the effects of pH and foreign ions, FTIR and XPS spectra analyses, the possible interaction mechanisms of U(VI) onto ZIFs were surface complexation and electrostatic interaction. Among them, ZIF-8 with Zn metal center and 2-methylimidazolate organic ligand had the best elimination capacity for U(VI) because of its large surface area, active metal ion and abundant nitrogen-containing groups (e.g., C–N, Zn–N and CN). Specially, the adsorption energy of ZIF-8-Zn2-UO22+ structure was −2.299 eV obtained by DFT calculation, illustrating that U(VI) and N atoms were formed the most stable bidentate coordination compounds. This paper highlights the effects of the hydroxylated metals, the functional groups of the imidazole ring on the elimination of U(VI), which can provide constructive suggestions for further adsorbent materials amelioration.

A reaction-and-assembly approach using monoamine zinc porphyrin for highly stable large-area perovskite solar cells

Inhibiting the irreversible escape of organic cations and iodide species in perovskite films is crucial for the fabrication of efficient and stable perovskite solar cells (PSCs). Here, we develop a reaction-and-assembly approach using monoamine zinc porphyrin (ZnP) to modify methylammonium (MA+) lead iodide perovskite film. The amine group in ZnP reacts with MA+ and I− ions to yield monoammonium zinc porphyrin (ZnP-H+I−). The resultant films show no escape of iodide when immersed in ether solutions. Measurements from space-charge limited currents and transient photoluminescence indicate the modified films have reduced density of defects. These results suggest the formed ZnP-H+I− is bound on the surface and grain boundary of perovskite film to retard migrations of ions. DFT calculations also show that the energy alignment between ZnP-H+ and perovskite facilitates the electron transfer and reduces charge recombination at the perovskite grains. Furthermore, post-treating the ZnP-doped film with ZnP again results in the formation of a one dimension zig-zag coordination polymer on the surface of the perovskite film. The single crystal structure of ZnP shows the polymer layer is formed through the coordination interaction between the Zn(II) metal center and a neighboring monoamine. The polymer facilitates the interfacial charge transfer, and reduces the escape of organic cations and iodide species in perovskite films, thereby keeping the excellent cell performance (20.0%) and further realizing the ion encapsulation. Finally, the modified PSCs retain over 90% of its original efficiency over 2,000 h at 85 °C or AM 1.5 G continuous illumination, or over 6,000 h in 45% humidity without encapsulation. This work affords a new strategy to achieve the efficient ions immobilization and encapsulation by in situ reaction and coordination assembly of mono-amine zinc porphyrin.

Structural rigidity accelerates quantum decoherence and extends carrier lifetime in porphyrin nanoballs: a time domain atomistic simulation.

Nonradiative electron–hole (e–h) recombination is the primary source of energy loss in photovoltaic cells and inevitably, it competes with the charge transfer process, leading to poor device performance. Therefore, much attention has to be paid for delaying such processes; increasing the excitonic lifetime may be a solution for this. Using the real-time, density functional tight-binding theory (DFTB) combined with nonadiabatic molecular dynamics (NAMD) simulations, we demonstrate the exciton relaxation phenomena of different metal-centered porphyrin nanoballs, which are supposed to be very important for the light-harvesting process. It has been revealed that the carrier recombination rate gradually decreases with the increase in the molecular stiffness by introducing metal-coordinating templating agents into the nanoball. Our simulation demonstrates that the lower atomic fluctuations lead to poorer electron–phonon nonadiabatic coupling in association with weak phonon modes and these as a whole are responsible for shorter quantum coherence and hence delayed recombination events. Our analysis is in good agreement with the recent experimental observation. By replacing the Zn metal center with a heavier Cd atom, a similar trend is observed; however, the rate slows down abruptly. The present simulation study provides the fundamental mechanism in detail behind the undesired energy loss during exciton recombination and suggests a rational design of impressive nanosystems for future device fabrication.

Syntheses, characterizations, crystal structures, DFT/TD‐DFT, luminescence behaviors and cytotoxic effect of bicompartmental Zn (II)‐dicyanamide Schiff base coordination polymers: An approach to apoptosis, autophagy and necrosis type classical cell death

Two new Zn (II)‐dicyanamide (dca) 1‐D chain coordination polymers (CPs), [Zn (LOMe)(μ1‐dca)(μ1,5‐dca)]n(1)and [Zn (LOEt)(μ1‐dca)(μ1,5‐dca)]n(2)have been successfully synthesized from bicompartmental Schiff base ligands N,N′‐Bis(3‐methoxysalicylidenimino)‐1,3‐diaminopropane (H2LOMe), N,N′‐Bis(3‐ethoxysalicylidenimino)‐1,3‐diaminoproane (H2LOEt) respectively and structurally characterized using various spectroscopic protocols like1H NMR, IR, Raman, UV–Vis, fluorescence as well as elemental analysis, TGA, PXRD and SCXRD studies. X‐ray single crystal study revealed that both the complexes have two different geometrical arrangement of Zn metal centres with distorted square pyramidal Zn(2) and trigonal prismatic geometry Zn(1). Ab‐initio DFT (Density functional theory) has been executed at B3LYP (Becke, 3‐parameter, Lee‐Yang‐Parr) using DGDVP (Diffuse gradient double valence polarised) basis set to explain FMO (Frontier molecular orbital), TD‐DFT (Time‐dependent density functional theory) and photovoltaic efficiency in Dye Sensitized Solar Cell (DSSC). Hirshfeld surface (HS) and 2D fingerprint plot analyses are shed more light on the non‐covalent supramolecular interactions. The steady state and time‐resolved fluorescence measurements have been conducted in DMSO and solid‐state. CPs exhibited bi‐exponential decay in DMSO as well as solid‐state where fluorescence behaviors are mainly intra‐ligand (π → π*) in nature with lifetimes in the range (1.11–1.06 ns). In particular, in vitro cytotoxic activities were evaluated towards MCF7 (breast cancer) cell line, MDA‐MB‐231 (breast carcinoma) cell line and MCF10A (breast epithelial) cell line using MTT assay. CP1had lower cytotoxic effect against MCF7 (20 μM), MDA‐MB‐231 (15 μM) cell lines in comparison with cisplatin (42.2 ± 8, 128.2 ± 7 μM). CP1induced classical cell death apoptosis, autophagy and necrosis. Lower IC50value of CP1against MDA‐MB‐231 cell line provide new insights in the development of cancer therapeutics.

DFT Studies on Metal-Controlled Regioselective Amination of N-Acylpyrazoles with Azodicarboxylates.

Density functional theory calculations were carried out to study the reaction mechanisms of Ag(I)- and Zn(II)-catalyzed amination of unsaturated N-acylpyrazoles with azodicarboxylates. Our theoretical investigation focused on the origin of the metal-controlled regioselectivity (γ- versus α-amination). Through our calculations, it was found that the amination reactions occur via metal-dienolate intermediates, in which the Ag(I) center prefers to coordinate with the α-carbon or the pyrazolyl N-donor site of the dienolate ligand, while the Zn(II) center prefers to coordinate with the O-donor of the dienolate ligand. The different site preferences for coordination with dienolate between the Ag(I) and Zn(II) metal centers play the key roles in the different regioselectivity observed experimentally.

Syntheses, X-ray crystal structures of two new Zn(II)-dicyanamide complexes derived from H2vanen-type compartmental ligands: Investigation of thermal, photoluminescence, in vitro cytotoxic effect and DFT-TDDFT studies

Two new dicyanamide modulated zinc metal complexes [Zn4(LOMe)2(µ1-dca)2(µ1,5-dca)2] (1) and [Zn3(LOEt)2(H2O)(µ1-dca)(µ1,5-dca)] (2) have been synthesized using H2vanen-type compartmental ligands. Schiff base ligands and the complexes were characterized by means of elemental analyses, FT-IR, FT-Raman, UV–Visible, powder X-ray diffraction, TGA and fluorescence spectroscopy. Dicyanamide modulated Zn4/Zn3-nuclear metal complexes were structurally characterized by single crystal X-ray diffraction studies. In 1, the asymmetric Zn2-nuclear unit was ensembled with one fully deprotonated Schiff base ligand [LOMe]2− along with two dicyanamide ions where two structurally independent Zn(II) metal centers are found in the X-ray crystal structure. Single X-ray crystal structure confirmed the environment of Zn1 is distorted square pyramidal whereas Zn2 acquires distorted tetrahedral geometry. Unlike 1, in 2 three independent zinc metal centers have been identified as square pyramidal (Zn1), distorted trigonal bipyramidal (Zn2) and distorted tetrahedral (Zn3). 1 and 2 geometry were optimized using hybrid B3LYP functional with DGDZVP basis set to explain frontier molecular orbitals, molecular electrostatic potential and Hirshfeld surface (dnorm surfaces and 2D fingerprint plots). The electronic UV–Vis properties were determined by TD-DFT approach. The steady state and time-resolved fluorescence properties have been explored in DMSO solution. 1 and 2 exhibit bi-exponential decay and intra-ligand (π → π*) fluorescence behaviors with lifetimes in the range (2.45–5.71 ns). In addition, complexes solid-state and different solvent-dependent absorption and fluorescence spectra have been reported. Finally, the cytotoxic effect of the investigated dicyanamide complexes against breast cancer cell line (MCF7) shows promising results which makes them prospective complexes for anticancer medicament studies.

Synthesis, X‐ray characterization and density functional theory studies of N6‐benzyl‐N6‐methyladenine–M(II) complexes (M = Zn, Cd): The prominent role of π–π, C–H···π and anion–π interactions

We report the synthesis and X‐ray characterization of the N6‐benzyl‐N6‐methyladenine ligand (L) and three metal complexes, namely [Zn(HL)Cl3]·H2O (1), [Cd(HL)2Cl4] (2) and [H2L]2[Cd3(μ‐L)2(μ‐Cl)4Cl6]·3H2O (3). Complex1consists of the 7H‐adenine tautomer protonated at N3 and coordinated to a tetrahedral Zn(II) metal centre through N9. The octahedral Cd(II) in complex2is N9‐coordinated to two N6‐benzyl‐N6‐methyladeninium ligands (7H‐tautomer protonated at N3) that occupy apical positions and four chlorido ligands form the basal plane. Compound3corresponds to a trinuclear Cd(II) complex, where the central Cd atom is six‐coordinated to two bridging μ‐L and four bridging μ‐Cl ligands. The other two Cd atoms are six‐coordinated to three terminal chlorido ligands, to two bridging μ‐Cl ligands and to the bridging μ‐L through N3. Essentially, the coordination patterns, degree of protonation and tautomeric forms of the nucleobase dominate the solid‐state architectures of1–3. Additionally, the hydrogen‐bonding interactions produced by the endocyclic N atoms and NH groups stabilize high‐dimensional‐order supramolecular assemblies. Moreover, energetically strong anion–π and lone pair (lp)–π interactions are important in constructing the final solid‐state architectures in1–3. We have studied the non‐covalent interactions energetically using density functional theory calculations and rationalized the interactions using molecular electrostatic potential surfaces and Bader's theory of atoms in molecules. We have particularly analysed cooperative lp–π and anion–π interactions in1and π+–π+interactions in3.

Purple acid phosphatase inhibitors as leads for osteoporosis chemotherapeutics

Purple acid phosphatases (PAPs) are metalloenzymes that catalyse the hydrolysis of phosphate esters under acidic conditions. Their active site contains a Fe(III)Fe(II) metal centre in mammals and a Fe(III)Zn(II) or Fe(III)Mn(II) metal centre in plants. In humans, elevated PAP levels in serum strongly correlate with the progression of osteoporosis and metabolic bone malignancies, which make PAP a target suitable for the development of chemotherapeutics to combat bone ailments. Due to difficulties in obtaining the human enzyme, the corresponding enzymes from red kidney bean and pig have been used previously to develop specific PAP inhibitors. Here, existing lead compounds were further elaborated to create a series of inhibitors with Ki values as low as ∼30 μM. The inhibition constants of these compounds were of comparable magnitude for pig and red kidney bean PAPs, indicating that relevant binding interactions are conserved. The crystal structure of red kidney bean PAP in complex with the most potent inhibitor in this series, compound 4f, was solved to 2.40 Å resolution. This inhibitor coordinates directly to the binuclear metal centre in the active site as expected based on its competitive mode of inhibition. Docking simulations predict that this compound binds to human PAP in a similar mode. This study presents the first example of a PAP structure in complex with an inhibitor that is of relevance to the development of anti-osteoporotic chemotherapeutics.

New zinc/tetradentate N4 ligand complexes: Efficient catalysts for solvent-free preparation of cyclic carbonates by CO2/epoxide coupling

Tetra-nitrogenated Zn-Schiff-base complexes have been synthetized and studied by X-ray diffraction. The prepared Zn-N4-ligands complexes could not follow the 18-electron rule. This property has allowed the complexes to be efficient in the coordination and activation of the substrates. The zinc complex of N,N’-bis(2-p-tosylaminobenzylidene)-1,2-diaminecyclohexane, Zn(Cy-Ts) combined to tetra-butylammonium iodide (TBAI) in a ratio of 1:1, or to triethylamine, catalyzed efficiently the CO2/epoxides coupling. These catalytic reactions were carried out without solvent at 120 °C under CO2 pressure. Cyclic carbonates were selectively obtained with high yield up to 99% (TON up to 4900). Two plausible pathways of CO2/epoxide coupling mechanism were proposed without halide intervention, where both reactants are activated by the same Zn metal center.

Combustion of energetic iodine-rich coordination polymer – Engineering of new biocidal materials

Development and molecular engineering of new highly-efficient energetic biocidal materials is a significant challenge and of a great importance. Until now this type of materials included mostly halogen-rich nano-thermites and iodine-rich organic materials. So far, no energetic coordination polymers were reported as precursors for combustion-generated biocidal agents. Here, we demonstrate for the first time the synthesis of uniquely-structured three-dimensional energetic coordination polymer (ECP3) containing Zn metal centers and iodine- and nitrogen-rich bridging ligand (2). Upon its combustion, ECP3 is capable of generating gaseous reactive iodine species and elemental iodine-coated ZnO particles. ECP3 presents a novel approach for the design of efficient biocidal agents.

"To Be or Not to Be" Protonated: Atomic Details of Human Carbonic Anhydrase-Clinical Drug Complexes by Neutron Crystallography and Simulation

Human carbonic anhydrases (hCAs) play various roles in cells, and have been drug targets for decades. Sequence similarities of hCA isoforms necessitate designing specific inhibitors, which requires detailed structural information for hCA-inhibitor complexes. We present room temperature neutron structures of hCA II in complex with three clinical drugs that provide in-depth analysis of drug binding, including protonation states of the inhibitors, hydration water structure, and direct visualization of hydrogen-bonding networks in the enzyme's active site. All sulfonamide inhibitors studied bind to the Zn metal center in the deprotonated, anionic, form. Other chemical groups of the drugs can remain neutral or be protonated when bound to hCA II. MD simulations have shown that flexible functional groups of the inhibitors may alter their conformations at room temperature and occupy different sub-sites. This study offers insights into the design of specific drugs to target cancer-related hCA isoform IX.

Theoretical and experimental insight into zinc loading on mesoporous silica

Zinc oxide species grafted on mesostructured cellular foam (MCF) silica are investigated using a combination of experimental and theoretical techniques. MCF is modelled using a realistic amorphous silica surface model surface slab. The most energetically favorable complexes grafted on the silica surface were identified and characterized at the molecular level. The Zn metal center was found in tetrahedral coordination. Moreover, the Si-O-Zn-OH species is found to be stabilized in a 5 fold coordinated silicon with an unusual trigonal bipyramidal geometry. A mechanism for the grafting process of the metal species on the support is proposed.

Five-Coordinate Zinc(II) Complex: Synthesis, Characterization, Molecular Structure, and Antibacterial Activities of Bis-[(E)-2-hydroxy-N′-{1-(4-methoxyphenyl)ethylidene}benzohydrazido]dimethylsulfoxidezinc(II) Complex

The titled Zn(II) complex was synthesized by reacting the compound (E)-2-hydroxy-N′-{1-(4-methoxyphenyl)ethylidene}benzohydrazide with zinc(II) acetate dihydrate in alkaline DMSO and ethanol solution under reflux condition for 28 hours. The resulting solid was filtered and recrystallized from the mixture of ethanol and DMSO. The hydrazone Schiff base and its Zn(II) complex were characterized using 1H, 13C NMR, FTIR, UV-Vis spectroscopy, and single crystal X-ray diffraction analysis. Meanwhile, their antibacterial activities were examined using disc diffusion method. The spectral studies showed that the hydrazone Schiff base underwent keto-enol tautomerization, forming a bidentate ligand (N,O) towards Zn(II) ion. Surprisingly, on top of the two hydrazone Schiff base molecules which coordinated to the Zn metal center, an additional DMSO molecule was found attached to the Zn metal center in the crystal data, resulting in a 5-coordinate distorted trigonal bipyramidal Zn(II) complex. Both hydrazone Schiff base and its Zn(II) complexes were found to exhibit low antibacterial activity even when the concentrations were increased to 800 ppm.

A two-fold interpenetrated metal-organic framework for the highly selective detection of explosive picric acid

A two-fold interpenetrated metal-organic framework{[Zn(bpydb)(H2O)](DMF)0.75} (1, DMF=N,N-dimethylformamide), involving the aromatic trigonal heterofunctional ligand 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid (bpydbH2) and Zn(II) metal center has been successfully synthesized under solvothermal condition. The structure of 1 was characterized by single-crystal X-ray diffraction, which shows a two-fold interpenetrated 3-connected framework with ThSi2-type topology. The luminescent sensing of different nitro-explosives was investigated, and the results indicated that 1 could behave as an effective sensor for detecting picric acid (PA) with high selectivity and sensitivity. Furthermore, the quenching mechanism has also been investigated in detail.

Copper(II), zinc(II) and nickel(II) coordination polymers using bidentate hyroxyphenyl-tetrazolyl ligand

Herein, we report various metal complexes containing {5-(2-hydroxy)phenyl}tetrazolyl (H2hptz) which form various high-dimensional coordination polymers in a crystalline solid state. A reaction of metal perchlorates, 2,2′-bipyrimidine (bpym), KOH, and tetrazolyl ligand (H2hptz) in H2O or N,N-dimethylmethanamide (DMF) yield 2-D [Cu(hptz)(bpym)]n (1), [Zn(hptz)(bpym)]n (2) and 3-D [K(bpym)2Ni(hptz)(H2O)2.5(OH)]n (3) coordination complexes with a high synthetic yield. These compounds were characterized by elemental analysis, IR spectroscopy, and single crystal X-ray crystallography. Cu2+ and Zn2+ complexes showed 2-D infinite network systems, forming coordination polymers (caused by extra bonding between metal ions and tetrazolyl). The environment of the Cu and Zn metal centers are quite similar; however, Zn2+ complexes have significantly shorter Zn–O bond distances with the hydroxyl group of other [Zn(hptz)(bpym)] unit. The Ni2+ complex 3 showed a completely different composition from that of complexes 1–2. Complex 3 showed 3-D structure based on octahedral units, which were composed of two hptz2− and one bpym ligands around the Ni center. These units infinitely repeat with K ions and water molecules along the a-, b-, and c-axes of the unit cells. Their magnetic behaviors were also studied.

Synthesis, Crystal Structure, and Fluorescent Properties of a 2D Zinc(II) Complex

The 2,2′-biphenyl-4,4′-dicarboxylate (H2bpy-4,4′-dc) and 2,2′-Bis(imidazol-1-ylmethyl)-biphenyl (bipb) have been selected as the bridging ligands. One zinc(II) MOF, [Zn(bpy-4,4′-dc)(bipb)]n has been successfully obtained by hydrothermal reaction and synthesis. The molecular structure has been elucidated by single-crystal X-ray diffraction. The complex possesses of 1D block chain [(bpy-4,4′-dc)2(bibp)2Zn4]. Taking advantage of the tetrahedral coordination preference of the Zn metal centers, the connected chains adopt a folding conformation to form a two-dimensional architecture. The complex was further characterized by IR spectroscopy, PXRD pattern, fluorescent spectra, and thermal stability measurements.

Coordination compounds of a hydrazone derivative with Co(iii), Ni(ii), Cu(ii) and Zn(ii): synthesis, characterization, reactivity assessment and biological evaluation

Increasing inhibitory effect of Zn-Hp2DAP < Hp2DAP < Co-Hp2DAP on ABC transporter MDR1 drug efflux pump.

Unexpected Emission Properties of a 1,8‐Naphthalimide Unit Covalently Appended to a Zn–Salophen

AbstractWe report the synthesis, characterization, and binding properties of a Zn–salophen complex, 1a, functionalized with a 1,8‐naphthalimide unit. Unexpectedly, the emission spectrum of 1a shows a remarkable quenching of the band assigned to the naphthalimide unit. To better understand this phenomenon, a supramolecular model system constituted by a symmetric Zn–salophen and a pyridyl derivative of 1,8‐naphthalimide, 1b·2a, was investigated. We propose the existence of a photoinduced energy transfer process between the naphthalimide (donor) and the salophen (acceptor) units in 1b·2a. A similar process must be operative in the covalent receptor 1a. Nevertheless, the results deriving from steady‐state fluorescence experiments do not rule out the occurrence of a photoinduced electron transfer process as alternative pathway for the quenching. We also describe the chemosensing properties of receptor 1a and the supramolecular system 1b·2a towards acetate. The nonsymmetrically substituted salophen receptor 1a only transduces the binding of the anion to the Zn metal center in significant spectroscopic changes in its absorption spectrum. On the other hand, we exploit the strong emission quenching experienced by the naphthalimide component in the supramolecular complex 1b·2a to detect anions (e.g. acetate) by means of a typical “turn‐on” fluorescent indicator displacement assay.

Thermodynamic Study of CO2 Sorption by Polymorphic Microporous MOFs with Open Zn(II) Coordination Sites.

Two Zn-based metal organic frameworks have been prepared solvothermally, and their selectivity for CO2 adsorption was investigated. In both frameworks, the inorganic structural building unit is composed of Zn(II) bridged by the 2-carboxylate or 5-carboxylate pendants of 2,5-pyridine dicarboxylate (pydc) to form a 1D zigzag chain. The zigzag chains are linked by the bridging 2,5-carboxylates across the Zn ions to form 3D networks with formulas of Zn4(pydc)4(DMF)2·3DMF (1) and Zn2(pydc)2(DEF) (2). The framework (1) contains coordinated DMF as well as DMF solvates (DMF = N,N-dimethylformamide), while (2) contains coordinated DEF (DEF = N,N-diethylformamide). (1) displays a reversible type-I sorption isotherm for CO2 and N2 with BET surface areas of 196 and 319 m(2)/g, respectively. At low pressures, CO2 and N2 isotherms for (2) were not able to reach saturation, indicative of pore sizes too small for the gas molecules to penetrate. A solvent exchange to give (2)-MeOH allowed for increased CO2 and N2 adsorption onto the MOF surface with BET surface areas of 41 and 39 m(2)/g, respectively. The binding of CO2 into the framework of (1) was found to be exothermic with a zero coverage heat of adsorption, Qst(0), of −27.7 kJ/mol. The Qst(0) of (2) and (2)-MeOH were found to be −3 and −41 kJ/mol, respectively. The CO2/N2 selectivity for (1), calculated from the estimated KH at 296 K, was found to be 42. At pressures relevant to postcombustion capture, the selectivity was 14. The thermodynamic data are consistent with a mechanism of adsorption that involves CO2 binding to the unsaturated Zn(II) metal centers present in the crystal structures.