Adsorption of molecular hydrogen on inorganometallic complexes B<Subscript>2</Subscript>H<Subscript>4</Subscript>M (M=Li,Be, Sc,Ti, V)

Molecular interaction between hydrogen molecules and B₂H₄M (M=Li, Be, Sc, Ti, V) complexes has been studied using the DFT method (M06 functional) and 6-311++G** basis set. The hydrogen uptake capacity of the complexes considered is higher than the target set by the US Department of Energy (5.5 wt% by 2020). The metal atom bound strongly to the B₂H₄ substrate. Adsorption of molecular hydrogen on Be-, Ti-, and V-decorated complexes is thermodynamically possible for all the pressures and temperatures considered whereas it is unfavorable for Li-decorated complexes for all the pressure and temperatures. For the Sc-doped complexes, adsorption of molecular hydrogen is favorable below 330 K and entire pressure range considered. All the H₂ adsorbed complexes are kinetically stable. For all the complexes, the interaction between the inorganometallic complexes and the H₂ molecules adsorbed is attractive whereas that between adsorbed H₂ molecules is repulsive. We have also performed molecular dynamics simulations to confirm the same number of H₂ molecule adsorption from the simulations and DFT calculations.     

Structure and Stability of (NG)nCN3Be3+ Clusters and Comparison with (NG)BeY0/+

The noble gas binding ability of CN₃Be₃⁺ clusters was assessed both by ab intio and density functional studies. The global minimum structure of the CN₃Be₃⁺ cluster binds with four noble‐gas (NG) atoms, in which the Be atoms are acting as active centers. The electron transfer from the noble gas to the Be atom plays a key role in binding. The dissociation energy of the Be? NG bond gradually increases from He to Rn, maintaining the periodic trend. The HOMO–LUMO gap, an indicator for stability, gives additional insight into these NG‐bound clusters. The temperature at which the NG‐binding process is thermodynamically feasible was identified. In addition, we investigated the stability of two new neutral NG compounds, (NG)BeSe and (NG)BeTe, and found them to be suitable candidates to be detected experimentally such as (NG)BeO and (NG)BeS. The dissociation energies of the Be? NG bond in monocationic analogues of (NG)BeY (Y=O, S, Se, Te) were found to be larger than in the corresponding neutral counter‐parts. Finally, the higher the positive charge on the Be atoms, the higher the dissociation energy for the Be? NG bond becomes.     

Verification of DFT-predicted hydrogen storage capacity of VC3H3 complex using molecular dynamics simulations

Density functional theory (DFT) and Fourth‐order Möller–Plesset (MP4) perturbation theory calculations are performed to examine the possibility of hydrogen storage in V‐capped VC₃H₃ complex. Stability of bare and H₂ molecules adsorbed V‐capped VC₃H₃ complex is verified using DFT and MP4 method. Thermo‐chemistry calculations are carried out to estimate the Gibbs free corrected averaged H₂ adsorption energy which reveals whether H₂ adsorption on V‐capped VC₃H₃ complex is energetically favorable, at different temperatures. We use different exchange and correlation functionals employed in DFT to see their effect on H₂ adsorption energy. Molecular dynamic (MD) simulations are performed to confirm whether this complex adsorbs H₂ molecules at a finite temperature. We elucidate the correlation between H₂ adsorption energy obtained from density functional calculations and retaining number of H₂ molecules on VC₃H₃ complex during MDs simulations at various temperatures. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Higher hydrogen uptake capacity of C2H4Ti+ than C2H4Ti: a quantum chemical study

Using density functionals theory, we show that gravimetric hydrogen uptake of C₂H₄Ti complex and its cation, C₂H₄Ti⁺, differ by about 2 wt%. Six and five hydrogen molecules are found to be adsorbed on C₂H₄Ti⁺ and C₂H₄Ti complexes thereby showing a hydrogen-uptake capacity of 13.74 and 11.72 wt%, respectively. All hydrogen molecules are adsorbed in molecular form on C₂H₄Ti⁺ ion with an increase in metal bond strength, whereas in some cases, the hydrogen molecules are found to be dissociated on C₂H₄Ti neutral complex. The uptake capacity of neutral C₂H₄Ti complex shown in this work is in excellent agreement with that reported experimentally, Phillips and Shivaram (Phys Rev Lett 100:105505, 2008). The H₂ adsorption energy and its dependence on exchange and correlation functions in density functionals method were illustrated. Even after the adsorption of maximum number of hydrogen molecules on C₂H₄Ti and C₂H₄Ti⁺ complexes, Ti and Ti⁺ remain strongly bound to C₂H₄ substrate.     

Noble‐Gas Complexes: Theoretical Investigation of Multicenter Polynuclear Species

Ab initio calculations at the MP2 level of theory disclose the conceivable existence of neutral complexes containing four or five distinct noble gases (Ng) each bound to a distinct Be‐atom. These multicenter polynuclear Ng molecules are formally obtained by replacing the H‐atoms of CH₄ and but‐2‐yne with ? NBeNg moieties, which behave as independent monovalent ‘functional groups’. Our investigated complexes include the five homotetranuclear [C(NBeNg)₄] complexes 1 – 5 (Ng=He? Xe), the five heterotetranuclear complexes [CN₄Be₄(He)(Ne)(Ar)(Kr)] ( 6 ), [CN₄Be₄(He)(Ne)(Ar)(Xe)] ( 7 ), [CN₄Be₄(He)(Ne)(Kr)(Xe)] ( 8 ), [CN₄Be₄(He)(Ar)(Kr)(Xe)] ( 9 ), and [CN₄Be₄(Ne)(Ar)(Kr)(Xe)] ( 10 ), and the heteropentanuclear complex [HC₄N₅Be₅(He)(Ne)(Ar)(Kr)(Xe)] ( 11 ). We also investigated the five model complexes [H₃CNBeNg] (Ng=He? Xe) containing a single ? NBeNg moiety. The geometries and vibrational frequencies of all these species, invariably characterized as minimum‐energy structures, were computed at the MP2(full)/6‐31G(d,p)/SDD level of theory, and their stability with respect to the loss of the various Ng‐atoms was evaluated by single‐point calculations at the MP2(full)/6‐311G(d)/SDD level of theory. The beryllium‐Ng binding energies range from ca. 17 (Ng=He) to ca. 63 (Ng=Xe) kJ/mol, and the results of natural‐bond‐orbital (NBO) and atoms‐in‐molecules (AIM) analysis reveal that the Be? Ng interaction is essentially electrostatic for helium, neon, argon, and krypton, and has probably a small covalent contribution for xenon.     

Wellenmechanische Untersuchungen an der Wasserstoffbrücke zwischen zwei Berylliumatomen

The systems Be₂H⁺ and Be₂H^? have been investigated for different nuclear positions, the H atom being situated between the Be atoms, taking all electrons into account, using the Allgemeines Programmsystem/SCF –MO –LC (LCGO ) Verfahren. For Be₂H⁺ there results a minimum total energy of ?29.3824 a.u. in the linear symmetric configuration with a bond distance of 1.609 Å. The ionization energy was estimated to be 12.37 eV. The formation of Be₂H⁺ can be interpreted as an addition of Be to BeH⁺ with an exotherm heat of reaction of 7.0 kcal/mole. The electron affinity of BeH⁺ (ionization energy of BeH) was estimated to be approximately 7.24 eV. All force constants of Be₂H⁺ and BeH⁺ have been computed. Using SCF results, the Be₂H^? was found to be unstable.     

Theoretical Study of Sticking Processes on Molecular Models of Silica Surfaces

The adsorption of small charged and neutral molecules on silica supports was modelled using perturbative post-Hartree–Fock quantum chemical methods (MP2 and MP4). The simplest spherosiloxane compound (H₄Si₄O₆) was used to mimic the surface while several molecules (namely CH₄, NH ₄ ⁺ , NH₃, OH ₃ ⁺ H ₃ ⁺ ) were considered as adsorbed species. Direct sticking of the molecules on one of the (Si–O)₃ ring leads to very different binding energies for cations (more than 11 kcal/mol) and neutral molecules (a few kcal/mol). These results indicate a dominant strong ion–multipole interaction for the first ones and a weak dispersion-type interaction for the latter. If the spherosiloxane cluster is screened by a mantle of accreted dust as it is the case in interstellar environment, the value of the binding energies, computed using the continuum dielectric theory, are predicted to be significantly reduced.     

From Very Strong to Inexistent Be−Be Bonds in the Interactions of Be2 with π-Systems

Isolated Be₂ is a typical example of a weakly bound system, but interaction with other systems may give rise to surprising bonding features. The interactions between Be₂ and a set of selected neutral C_nH_n (n=2–8) π-systems have been analyzed through the use of G4 and G4MP2 ab initio methods, along with multireference CASPT2//CASPT2 calculations. Our results systematically show that the C_nH_n−Be₂−C_nH_n clusters formed are always very stable. However, the nature of this interaction is completely different when the π-system involved is a closed shell species (n=2, 4, 6, 8), or a radical (n=3, 5, 7). In the first case, the interaction does not occur with the π-system as a whole, but with specific C centers yielding rather polar but strong C−Be bonds. Nonetheless, although the Be−Be distances in these complexes are similar to the ones in compounds with ultra-strong Be−Be bonds, a close examination of their electron density distribution reveals that no Be−Be bonds exist. The situation is totally different when the interaction involves two π-radicals, C_nH_n−Be₂−C_nH_n (n=3, 5, 7). In these cases, a strong Be−Be bond is formed. Indeed, even though Be is electron deficient, the Be₂ moiety behaves as an efficient electron donor towards the two π-radicals, so that the different C_nH_n−Be₂−C_nH_n (n=3, 5, 7) clusters are the result of the interaction between Be₂²⁺ and two L⁻ anions. The characteristics of these two scenarios do not change when dealing with bicyclic π-compounds, such as naphthalene and pentalene, because the interaction with the Be₂ moiety is localized on one of the unsaturated cycles, the other being almost a spectator.     

Ligand Exchange Processes on Solvated Beryllium Cations V. Water Exchange on [Be(X)(H2O)3]+ (X: H–,F–, Cl–, Br–, OH–, CN–, NCNCN–)‡

The water exchange reaction of Be^II complexes in the series [Be(X)(H₂O)₃]⁺ (X = H^–, F^–, Cl^–, Br^–, OH^–, CN^–, NCNCN^–) was studied by DFT calculations (RB3LYP/6‐311+G**) and identified as an associative interchange mechanism. The influence of X on the activation energies was examined and found to be largely negligible, thus making them all act as spectator ligands. The energies for addition of a fourth water molecule, representing the second coordination sphere, were approximately half of that found for similar dicationic complexes and close to that found for monocationic species like [Li(H₂O)₄]⁺.     

Beryllium-9 NMR Spectroscopy and Molecular Orbital Studies of Hydrogen-Bonding Interaction of Tetraaquaberyllium(II) Ion with Water in the Second Solvation Sphere in Propiononitrile

The equilibrium constants of the hydrogen-bonding interactions between the tetraaqua-beryllium(II) ion ([Be(H₂O)₄]²⁺) and water in the second solvation sphere were determined from the dependence of the ⁹Be NMR chemical shift (δ_Be) on the water concentration (C _W) in propiononitrile (PN). The ⁹Be NMR line assigned to [Be(H₂O)₄]²⁺ is downfield shifted with the increasing C _W, and the change in δ_Be as a function of C _W is explained in terms of a two-step hydrogen-bonding interaction to form [Be(H₂O)₄](H₂O) _n ²⁺ (n = 1, 2). Molecular orbital calculations for [Be(H₂O)₄](H₂O) _n ²⁺ (n = 0?2) revealed that the electron density on the Be(II) ion increases with an increase in n due to an enhanced polarization of the bound water molecules accompanied by the hydrogen bonding in the second solvation sphere. The observed downfield shift of δ_Be is interpreted as a significant compensation of the diamagnetic upfield shift by the paramagnetic contribution due to the mixing of the vacant s and p orbitals of Be with the σ-type lone-pair orbitals of the coordinating water molecules.     

[Be3(μ3‐O)3(MeCN)6{Be(MeCN)3}3](I)6 – ein Berylliumkomplex mit Cyclo‐(Be3O3)‐Kern und sein Hydrolyseprodukt [Be(H2O)4](I)2·2MeCN

Single crystals of [Be₃(μ₃‐O)₃(MeCN)₆{Be(MeCN)₃}₃](I)₆·4CH₃CN ( 1 ·4CH₃CN) were obtained in low yield by the reaction of beryllium powder with iodine in acetonitrile suspension, which probably result from traces of beryllium oxide containing the applied beryllium metal. The compound 1 ·4CH₃CN forms moisture sensitive, colourless crystal needles, which were characterized by IR spectroscopy and X‐ray diffraction (Space group Pnma, Z = 4, lattice dimensions at 100(2) K: a = 2317.4(1), b = 2491.4(1), c = 1190.6(1) pm, R₁ = 0.0315). The hexaiodide complex cation 1 ⁶⁺consists of a cyclo‐Be₃O₃ core with slightly distorted chair conformation, stabilized by coordination of two acetonitrile ligands at each of the beryllium atoms and by a {Be(CH₃CN)₃}²⁺ cation at each of the oxygen atoms. This unique coordination behaviour results in coplanar OBe₃ units with short Be–O distances of 155.0 pm and 153.6 pm on average of bond lengths within the cyclo‐Be₃O₃ unit and of the peripheric BeO bonds, respectively. Exposure of compound 1 ·4CH₃CN to moist air leads to small orange crystal plates of [Be(H₂O)₄]I₂·2CH₃CN ( 3 ·2CH₃CN). According to the crystal structure determination (Space group C2/c, Z = 4, lattice dimensions at 100(2) K: a = 1220.7(1), b = 735.0(1), c = 1608.5(1) pm, β = 97.97(1)°, R₁ = 0.0394), all hydrogen atoms of the dication [Be(H₂O)₄]²⁺ are involved to form O–H ··· N and O–H ··· I hydrogen bonds with the acetonitrile molecules and the iodide ions, respectively. Quantum chemical calculations (B3LYP/6‐311+G**) at the model [Be₃(μ₃‐O)₃(HCN)₆{Be(HCN)₃}₃]⁶⁺ show that chair and boat conformation are stable and that the distorted chair conformation is stabilized by packing effects.     

Correlated polarization propagator calculations of static polarizabilities

We present a systematic comparison of the correlation contribution at the level of the second-order polarization propagator approximation (SOPPA ) and MP 2 to the static dipole polarizability of (1) Be, BeH^?, BH, CH⁺, MgH^?, AIH, SiH⁺, and GeH⁺; (2) BH₃, CH₄, NH₃, H₂O, HF, BF, and F₂; and (3) N₂, CO, CN^?, HCN, C₂H₂, and HCHO . Fairly extended basis sets were used in the calculations. We find that the agreement with experimental values is improved in SOPPA and MP .2 over the results at the SCF level. The signs and magnitudes of the correlation contribution in SOPPA are similar to those obtained in analytical derivative MP 2 calculations. However, it is not possible to say, in general, which method gives the largest correlation contribution or the best agreement with experiment, nor is it possible to make a priori prediction of the sign of the correlation contribution. For the first group of molecules, which have a quasi-degenerate ground state, additional CCDPPA and CCSDPPA calculations were performed and compared with polarizabilities obtained as analytical/numerical derivatives of the CCD and CCSD energies. The CCSDPPA results were found to be in better agreement with other calculations than were the SOPPA results, demonstrating the necessity of using methods based on infinite-order perturbation theory for these systems. © 1994 John Wiley & Sons, Inc.     

H2-induced CO adsorption and dissociation over Co/Al2O3 catalyst

The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.     

The behaviour of beryllium μ4-oxo-μ-carboxylates under electron impact

The electron impact mass spectra of eight polynuclear beryllium complexes Be₄O(RCO₂)₆ (R?H, CH₃, C₂H₅) and Be₄O(RCO₂)₅OR′ (R?CH₃, R′?H, CH₃, C₂H₅, C₃H₇; R?C₂H₅, R′?C₂H₅) are reported. The major fragmentations involve the elimination of (RCO)₂O (RCOOR′) or Be(RCO₂)₂ (Be(RCO₂)OR′) from the ions [M? L]⁺ and of {(R? H)CO}, (R′? H), H₂O and BeO from the lighter ions. The fragmentation patterns are practically independent of the organic groups present and can be rationalized by stereochemical considerations.     

Water exchange rates and mechanisms in tetrahedral [Be(H2O)4]2+ and [Li(H2O)4]+ complexes using DFT methods and cluster‐continuum models

The water exchange reactions in aquated Li⁺ and Be²⁺ ions were investigated with density functional theory calculations performed using the [Li(H₂O)₄]⁺·14H₂O and [Be(H₂O)₄]²⁺·8H₂O systems and a cluster‐continuum approach. A range of commonly used functionals predict water exchange rates several orders of magnitude lower than the experimental ones. This effect is attributed to the overstabilization of coordination number four by these functionals with respect to the five‐coordinated transition states responsible for the associative ( A ) or associative interchange ( I_a ) water exchange mechanisms. However, the M06 and M062X functionals provide results in good agreement with the experimental data: M062X/TZVP calculations yield a concerted I_a mechanism for the water exchange in [Be(H₂O)₄]²⁺·8H₂O that gives an average residence time of water molecules in the first coordination sphere of 260 μs. For [Li(H₂O)₄]⁺·14H₂O the water exchange reaction is predicted to follow an A mechanism with a residence time of inner‐sphere water molecules of 25 ps.     

Die Deprotonierung von Metall-Aquoionen I.: Be · aq2+ Solvatations-Isomerie

The reaction of Be · aq²⁺ with OH^? leeds not only to loss of protons by the metalaquo ion but also to structural changes in the solvation sphere. These can be studied by following the pH variations during the first decisecond after mixing the solutions of metal salt and alkali hydroxide. The equilibrium Be²⁺ ? BeOH⁺ is reached within 5 milliseconds if acid free Beryllium solutions are used. If the metal solution is strongly acidic, however, the establishment of the equilibrium needs more time because of the slowness of the process H⁺ + BeOH⁺ → Be²⁺ (k ～ 10⁵ M^?1, s^?1). The extraction of two protons produces in the first instance an unstable Be(OH) species which transforms into the stable isomer Be(OH)₂ (solvatation isomerism) in a first-order reaction of half-life of 7 ms. This isomerisation causes almost complete disappearance of BeOH⁺ from the equilibrium Be²⁺ ? BeOH⁺ ? Be(OH)₂. (KAKIHANA & SILLEN state that the relaxed solutions contain only Be²⁺, Be(OH)₂, Be₃(OH) and some Be₂OH³⁺.) The formation of the polynuclear species Be₃(OH) needs about 30 seconds to go to completion.     

The Beryllium Pentamer: Trailing an Uneven Sequence of Dissociation Energies

Recent high‐resolution spectroscopic studies by Merritt, Bondybey, and Heaven (Science 2009 , 324, 1548) have heightened the anticipation that small beryllium clusters will soon be observed in the laboratory. Beryllium clusters are important discrete models for the theoretical study of metals. The trigonal bipyramidal Be₅ molecule is studied using high‐level coupled cluster methods. We obtain the optimized geometry, atomization and dissociation energies, and vibrational frequencies. The c～CCSDT(Q) method is employed to compute the atomization and dissociation energies. In this approach, complete basis set (CBS) extrapolations at the CCSD(T) level of theory are combined with an additive correction for the effect of iterative triple and perturbative quadruple excitations. Harmonic vibrational frequencies are obtained using analytic gradients computed at the CCSD(T) level of theory. We report an atomization energy of 129.6 kcal mol^?1 at the trigonal bipyramid global minimum geometry. The Be₅→Be₄+Be dissociation energy is predicted to be 39.5 kcal mol^?1. The analogous dissociation energies for the smaller beryllium clusters are 64.0 kcal mol^?1 (Be₄→Be₃+Be), 24.2 kcal mol^?1 (Be₃→Be₂+Be), and 2.7 kcal mol^?1 (Be₂→Be+Be). The trigonal bipyramidal Be₅ structure has an equatorial–equatorial bond length of 2.000 Å and an axial–equatorial distance of 2.060 Å. Harmonic frequencies of 730, 611, 456, 583, 488, and 338 cm^?1 are obtained at the CCSD(T)/cc‐pCVQZ level of theory. Quadruple excitations are found to make noticeable contributions to the energetics of the pentamer, which exhibits a significant level of static correlation.     

Ethylene and propylene adsorption and the formation of hydrocarbon complexes with NO2 upon interaction of adsorbed olefins with an NO + O2 mixture over HZSM-5 and CuZSM-5 zeolites studied by TPD and ESR

Adsorption of C₂H₄ and C₃H₆ on copper in oxidized samples of CuZSM-5 is found to increase with the copper concentration; simultaneously, olefin adsorption on the Br?nsted acid sites decreases. The Cu²⁺ cations in the square-planar coordination exhibit higher reactivity in olefin adsorption than copper cations in the square-pyramidal coordination. Thermal treatment of CuZSM-5 with hydrogen results in regeneration of the Br?nsted acid sites for olefin adsorption and the disappearance of Cu²⁺ cations, the active sites of adsorption, due to the reduction of Cu²⁺ to Cu⁺ and Cu⁰. Desorption peaks appear in the TPD spectra upon the interaction between the adsorbed hydrocarbons and NO₂. These peaks are not observed upon separate adsorption of the reactants, and they are likely due to decomposition of NO₂-hydrocarbon complexes over both the Br?nsted and copper-containing sites of the zeolite     

Hydrogen bonding between a water molecule and electronegative additives (O or Cl) on a Pt(111) surface

Water adsorption on Pt(111) surfaces treated with oxygen or hydrogen chloride at 20 K has been studied by Fourier transform infrared spectroscopy and scanning tunneling microscopy. Water molecules chemisorb predominantly on the sites of the electronegative additives (O or Cl^-), forming hydrogen bonds of O-HO or O-HCl^-. On a Pt(111)-2×2-O surface, water adsorption produces species (O(D₂O)), monomeric water (D₂O), (O(D₂O)₂) and ring tetramer-like cluster (O(D₂O)₃) on a Pt(111) surface. On a Pt(111)-3×3-Cl^- (θ=0.44) surface, water adsorption gives rise to a Pt(111)-(4×2)-(H₃O⁺+Cl^-) co-adsorption structure to form a hydrogen-bonding network between Cl^- and H₃O⁺ ions.     

Multiscale Computational Study on the Adsorption and Separation of CO2/CH4 and CO2/H2 on Li+‐Doped Mixed‐Ligand Metal–Organic Framework Zn2(NDC)2(diPyNI)

The quantum mechanics (QM) method and grand canonical Monte Carlo (GCMC) simulations are used to study the effect of lithium cation doping on the adsorption and separation of CO₂, CH₄, and H₂ on a twofold interwoven metal–organic framework (MOF), Zn₂(NDC)₂(diPyNI) (NDC=2,6‐naphthalenedicarboxylate; diPyNI=N,N′‐di‐(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide). Second‐order Moller–Plesset (MP2) calculations on the (Li⁺–diPyNI) cluster model show that the energetically most favorable lithium binding site is above the pyridine ring side at a distance of 1.817 Å from the oxygen atom. The results reveal that the adsorption capacity of Zn₂(NDC)₂(diPyNI) for carbon dioxide is higher than those of hydrogen and methane at room temperature. Furthermore, GCMC simulations on the structures obtained from QM calculations predict that the Li⁺‐doped MOF has higher adsorption capacities than the nondoped MOF, especially at low pressures. In addition, the probability density distribution plots reveal that CO₂, CH₄, and H₂ molecules accumulate close to the Li cation site. The selectivity results indicate that CO₂/H₂ selectivity values in Zn₂(NDC)₂(diPyNI) are higher than those of CO₂/CH₄. The selectivity of CO₂ over CH₄ on Li⁺‐doped Zn₂(NDC)₂(diPyNI) is improved relative to the nondoped MOF.