Novel 2D micro-porous Metal-Organic Framework for hydrogen storage

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Novel 2D micro-porous Metal-Organic Framework for hydrogen storage Zeynel Ozturk a,*, Dursun Ali Kose b, Zarife Sibel Sahin c, Goksel Ozkan d, Abdurrahman Asan a a

Hitit University, Department of Chemical Engineering, 19030, Corum, Turkey Hitit University, Department of Chemistry, 19030, Corum, Turkey c Sinop University, Department of Energy System Engineering, 57000, Sinop, Turkey d Department of Chemical Engineering, Gazi University, 06520, Ankara, Turkey b

article info

abstract

Article history:

A novel two dimensional Metal-Organic Framework (MOF) structured compound with tri-

Received 26 November 2015

mesic acid (TMA), 1,10 Phenantroline (Phen) and Cu(II) building blocks were synthesized

Received in revised form

and characterized experimentally. Then Grand Canonical Monte Carlo (GCMC) simulation

8 February 2016

calculations used for determination of hydrogen adsorption capacity and surface charac-

Accepted 18 May 2016

teristics of the compound theoretically. Three different regions were determined for the

Available online xxx

adsorbent, which were micro, micro/sub-meso spaces inside the adsorbent and the surface regions. It is found that the synthesized compound could uptake approx. 1.3 and 1.2 wt.%

Keywords:

hydrogen at 77 K, 100 bars and 1 bar respectively. Thus the adsorbent that is synthesized in

Hydrogen storage

this work have strong hydrogen adsorption capability in comparison to the previously

2D MOFs

reported ones.

Molecular simulation

© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Introduction Many energy systems are investigated as an alternative for the existing energy systems in the past decades. One of the most promising alternatives, hydrogen energy systems, have some barriers for common usage. Storing hydrogen efficiently in the perspective of storage performance, economy, and other criteria is a barrier that is needed to be passed. Using MetalOrganic Framework (MOF) structured materials, which consist of metal/metal clusters and organic ligands as linkers [1,2], is one of the promising candidates for efficient hydrogen storage.

MOFs have many advantages with their tunable structures and pores, thus single ligand and mixed ligand crystalline forms are also possible. MOF-5 (Zn4O(BDC)3, where BDC2
¼ 1,4benzenedicarboxylate) [3], MOF-177 (Zn4O(BTB)2, where BTB3
¼ 1,3,5-benzenetribenzoate) [4], and NU-100 (Cu3(ttei), where ttei ¼ 5,50 ,500 -(((benzene-1,3,5-triyltris(ethilene-2,1-diyl)) tris(benzene-4,1-diyl))tris(etilene-2,1-diyl)) triisophthalate) [5] are some of famous MOF structured compounds which have one ligand as building block inside. MOF-210 (Zn4O(BTE)(BPDC), where BTE3
¼ 4,40 ,400 -[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)] tribenzoate and BPDC2
¼ biphenyl-4,40 -dicarboxylate) [6], SNU50 (Cu2(abtc)(DMF)2 where abtc; azobenzene-3,30 ,5,50 -tetracarboxylate and DMF; di methyl formamide) [7] and without an

* Corresponding author. Tel.: þ90 532 653 62 12. E-mail addresses: [email protected] (Z. Ozturk), [email protected] (D.A. Kose), [email protected] (Z.S. Sahin), [email protected] (G. Ozkan), [email protected] (A. Asan). http://dx.doi.org/10.1016/j.ijhydene.2016.05.170 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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abbreviation Cu2(bdc)(dabco) (where bdc; benzene-1,4dicarboxylate and dabco; 1,4-diazobicyclo [2.2.2] oktane) [8] are some examples of mixed ligand MOFs. According to IUPAC [9], MOFs are described as 1, 2, or 3 dimensional network polymers extending through coordination bonds. The number of coordination network dimension increases the thermal stability of the final compound, as expected. In another point of view, it is able to construct two or three dimensional coordination polymers in thermally aided synthesize procedures [10e13]. Hydrogen can be stored in different medias through physical adsorption, or physisorption. Spillover has a big impact on hydrogen storage capacity and on the importance of porosity. Open metal sites inside the compounds act like a metal additive which increases the spillover effect of hydrogen. Li and Yang [14,15] reported that the platinum loaded activated carbon which enables more open metal sites for spillover, and platinum loaded activated carbon doped IRMOF-1 and IRMOF-8 could store 5e8 times more hydrogen in comparison to un-doped structures. Similarly, soc (square octahedral cubic) topology provides more open metal sites inside the MOFs, consequently mentioned sites increase the stored amount [16]. Zhou and co-workers [17] explained the effect of metal kind on open metal sites and their relations with hydrogen storage; the effect of open magnesium metal sites on hydrogen storage properties were investigated by Sumida et al. [18]. Hydrogen storage properties of the materials can be investigated by using molecular simulation calculations, in addition to experimental techniques. GCMC (Grand Cannonical Monte Carlo) ensemble [19] is commonly used to simulate hydrogen storage properties by physisorption. Interactions between hydrogen and host materials examined through GCMC by calculating possible positions of the hydrogen molecules, statistically [20,21]. Force field based GCMC calculations have been used for investigating hydrogen storage properties [22e24]. Yang and Zhong [25] calculated gas adsorption properties of MOF-5 in the gas mixture by using a special force field, TraPPE (transferable potentials for phase equilibria) [26] with GCMC. MOFs are able to uptake huge amounts of hydrogen with their high surface area. On the one hand, surface area plays an important role on hydrogen storage for highly porous adsorbents, on the other hand electrical charges (or spillover) of the metal centers or clusters inside are more effective for adsorbents that have small accessible surface areas [27e29]. Both phenomena effect the adsorption energy and it can be calculated using SA-MC (Simulated Annealing-Monte Carlo) simulations. Kim et al. [30] reported adsorption energies and population analysis of the interaction energies porphyrin based covalent organic polyhedral for hydrogen adsorption theoretically using SA-MC. A novel two dimensional MOF structured compound synthesized and the crystal structure determined experimentally in this work. Then the determined crystal structure used for simulating hydrogen storage and other characteristic calculations. At the final, hydrogen storage properties, surface area and characteristic of synthesized compound determined theoretically. Theoretical investigation of hydrogen adsorption characteristics of experimentally synthesized, and

characterized compound is the aim in this work. Therefore the gravimetric hydrogen uptake capacities at 77e298 K and 1e100 bar pressures, BET surface area, and pore size distribution calculations realized by using simulated hydrogen and nitrogen adsorption data after determination of the crystal structure experimentally. Surface characteristics and adsorption energies also calculated by using SA-MC for vacuum slab constructed on the surface of the compound in (0 0
1) plane.

Experimental and computational methods Synthesize The reactants were purchased from SigmaeAldrich (St. Louis, MO) and no purification applied for synthesis. The MOF structured compound synthesized according to solvothermal method in a teflon lined steel autoclave by using 2 mmol (0.4832 g) Cu(NO3)2$3H2O, 2 mmol (0.3640 g) 1,10phenantroline (Phen) and 1 mmol (0.2212 g) trimesic acid (TFA). According to synthesize procedure, reactants moved to a teflon pot which included 50 mL of anhydrous methanol, and then waited for 2 days at 105  C in an oven. Then the steel autoclave cooled to room temperature itself and blue crystals collected. Final product washed with ultra-pure water and methanol several times then dried at 85  C overnight.

Characterization Single crystal XRD data collection performed on D8-QUEST diffractometer equipped with a Mo-Ka radiation source at 296 K. The SHELXS-97 [31] software was used for the structure solution by direct method and then the structure refined by full-matrix least-squares methods on F2 using SHELXL-97 in WINGX suite [32]. All non-atoms were refined with anisotropic parameters. Phenyl hydrogen atoms were located from different maps and then treated as riding atoms with CeH distances of 0.93
A. All other H atoms were located in a difference map and refined freely. Determined molecular structures were created using MERCURY [33]. Supramolecular analyses were made and the diagrams aided by using PLATON [34]. Experimental FT-IR spectrums in 400e4000 cm
1 range (Perkin Elmer, Spectrum One; Waltham, MA) realized to support crystal structure which are determined by using single crystal XRD data. Also, the thermal analysis realized up to 900  C temperature (Shimadzu, DTG 60H, Nakagyoku, Kyoto, Japan) to determine thermal stability of the compound.

Computational method Hydrogen and nitrogen adsorption characteristics of MOF structured compound simulated to determine hydrogen storage capacity, BET surface area and pore size distribution theoretically. Molecular hydrogen interactions with the host material calculated with GCMC ensemble metropolis method that is described by Hastings [35]. Also the modified LenardJones (LJ) 12-6 parameters used for calculations that describes the intermolecular interactions. In the calculations,

Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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hydrogen and nitrogen molecules were set as a single van der Waals (vdW) site, in the other word, united atom model was used which was described by Poirier [36] in detail. The LJ 12-6 parameters for nitrogen and hydrogen were modified because the quantum effect at low temperatures such like 77 K. So, the temperature dependent quantum effects (Feyman-Hibbs effective potentials) for low temperature calculations in GCMC that the details described by Dimitrakakis et al. [37] was used to modify LJ parameters. The modified parameters for hydrogen molecule was 0.05988 kcal/mol and 3.4394
A which are descried in detail by Fischer et al. [38]. Similarly, LJ 12-6 parameters changed to 0.074 kcal/mol and 3.31
A for nitrogen interactions which are calculated and corrected by Liu et al. [39]. LJ 12-6 parameters for other elements were exactly the same with universal force field parameters that was described and created by Rappe et al. [40]. 30 fugasity steps used to calculate total amount of hydrogens and adsorption isotherms in logarithmic scale both for nitrogen and hydrogen in the simulation calculations. And then, excess amount of adsorbed hydrogens were calculated by using Eq. (1) which was described by Zhu et al. [41]. mexcess ¼ mtotal
rðT; PÞ$Vfree

(1)

where Vfree is the free volume, mexcess and mtotal represents the excess and total amount of adsorbed hydrogen, and r(T,P) is the density of hydrogen which are collected from the standart tables of NIST [42]. Kelvin equation based BJH pore size distribution which was described by Barret et al. [43] used to determine pore characteristics. In addition hydrogen and surface interaction calculations between synthesized compound and hydrogen molecules calculated by using SA-MC at 77 K and 298 K temperatures within 10 cycles and 100 000 calculation steps for each cycle under MC algorithms [30]. Isosteric heat (Qst) of hydrogen adsorption calculated for each gravimetric uptakes in Simulated Annealing task which was described by Kirkpatric et al. [44] and Cerny´ [45]. Also the Classius-Clapeyron equation [46] which is given in Eq. (2) was the basics of the adsorption heat calculations. " # vðLnPÞ   Qst ¼
R v T1

(2)

where P, R and T represents partial pressure, gas constant and temperature respectively. Energy distribution, also called population analysis of the interaction energies, of hydrogen adsorption inside and on the surface which was created on (0 0
1) plane as a vacuum slab of adsorbent was simulated with Simulated Annealing task [44,45].

Results and discussion The X-ray single crystal study shows that complex has 2D coordination polymer by the way it is possible to call it MOF (Crystal structure refinement parameters given in SI: Table 1 in detail). The asymmetric unit of the complex consists of a Cu(II) ion, one phen (phenanthroline) ligand, a half TMA (1,3,5-benzenetricarboxylic) ligand, two and a half

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crystal water molecules and one hydroxo group (Fig. S1 in supplementary information (SI) section). Each Cu1 atom is a distorted square pyramidal geometry with the t value of 0.291 [t ¼ (175.59e158.13)/60] (t ¼ 0 for an ideal square-pyramid, t ¼ 1 for an ideal trigonalbipyramid) [47]. The equatorial coordination comes from two oxygen atoms [O1 and O4] and two nitrogen atoms [N1 and N2], while the apical position is occupied by one oxygen atom [O3iii] of a TMA ligand [(iii) A
xþ3/2, yþ1/2,
zþ1/2]. The Cu1/Cu1iv separation is 3.366
[48]. The TMA ligand adopt m4-bridging coordination mode to connect four individual Cu(II) ions. The hydroxo group is located at a general position and bridges two neighboring Cu(II) ions. The CueN bond lengths are 2.017(2) and 2.039(2)
A, while the CueO bond lengths are 1.8995(11), 1.9675(16) and 2.2450(17), respectively (SI: Table S2). The Cu(II) ions are bridged by three TMA ligands to generate [Cu4(TMA)3OH] metalloligands. These [Cu4(TMA)3OH] metalloligands are connected with Cu2CO3 rings, generating 2D coordination polymer which is shown in Fig. 1. The Cu(II)/Cu(II) separations are 8.560
A and 9.763
A [49]. The 2D coordination polymer is supported by OeH/O hydrogen bonds and p/p interactions (details of these interactions are given in SI: Tables S3 and S4). Each Cu(II) center is six-connected with Schlafli vertex symbol of {3.5.122}; this connected node was analyzed using OLEX [50] (different views of the crystal structure given in SI: Fig. S2). Characteristic FT-IR peaks (Fig. S3 in SI) used to prove COO
coordination to the metal centers if they are mono-dentate or bi-dentate according to difference between symmetric and asymmetric stretching peaks. Nakamoto [51] reported that if the difference bigger than 150, bond order could be single (mono-dentate) otherwise double. The difference calculated 267 so the bond order was single as it is determined from single crystal-XRD (Fig. S1 in SI). Also the aqua molecule existence appointed from the IR spectra. Free aqua molecules were removed from the crystal structure for surface characterization and hydrogen storage calculations because degas pre-process have been applied to adsorbents in the real measurement systems. The aim of the degas was to remove non-bonded water molecules for thermal stability. It is also clear that the compound was still stable at the degas temperatures (105  C, thermal decomposition curves given in SI: Fig. S4). Then, empty spaces inside the adsorbent material (synthesized compound) was simulated and shown in Fig. 2a. Gray surfaces represent outer sites of the spaces that the hydrogen could be filled in while the blue surfaces were inner sites at the same figure. In the other word, outer sites of the empty spaces were occupied by the atoms of compound (more views given in SI: Fig. S5). Nitrogen adsorption isotherm was collected at 77 K and up to 1 bar and given in Fig. 2b. According to IUPAC classifications [52], nitrogen adsorption isotherm was Type-I which represents micro porosity. Pore size distribution (PSD) also proves the microporosity inside the adsorbent with 20
A mean pore width (Fig. 2c). Deviation for nitrogen adsorption isotherm from the ordinary curve between 0.1 and 0.5 relative pressures was the result of meso-pores inside the adsorbent that is also seen in PSD in Fig. 2c. It is clear that the adsorbent have one main pore and two small pores inside which results three peaks in PSD curve (given in Fig. 2c). The mentioned peaks are marked with

Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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Fig. 1 e Infinite 2D layer (a) with and (b) without Phen groups coordinated to compound.

yellow circles (in the web version) (I, II and III) and linked to related peaks in Fig. 2. BET surface area was calculated as 217 m2/g for degassed compound by using nitrogen adsorption simulation data. It resulted in a mean even low surface area in comparison to most known MOF structured compounds. For instance the surface areas of MOF-5 and MOF-210 were 3480 and 6240 m2/g reported by Furukawa et al. [6]. But it is clear that the surface area was not only parameter effects the hydrogen storage capacity. It is why the hydrogen storage capacities calculated for the synthesized adsorbent. Gravimetric and volumetric hydrogen storage capacity of the compound were calculated by using hydrogen adsorption simulation data, the uptake curves given in Fig. 3. It is found out that the compound could uptake more than 90% of its capacity up to 1 bar, as it is expected from Type-I adsorption isotherm. In addition a meaningful difference was not found

between excess and total uptake capacities for compound in the 0e1 bar pressure range. It is why the pore walls were filled by hydrogen molecules even in low pressures. Further, the more hydrogen only could be filled to the empty spaces of the pores with inter-molecular interactions between free hydrogen molecules and hydrogens placed on the pore walls. Hence the excess hydrogen value which was described by Frost et al. in detail [53] was calculated for higher pressures. It is found that the synthesized MOF structured compound could uptake 1.382 total and 1.191 excess wt.% hydrogen at 77 K and 100 bars pressure (Fig. 3a). Volumetric hydrogen uptake capacity was 170.02 mL/g for the same conditions. Total and excess hydrogen storage gravimetric percentages were 1.287 and 1.285 respectively at 77 K and 1 bar while the volumetric capacity was 158.36 mL/g at the same conditions. The difference between total and excess capacities was approx. 13% at 100 bars while the value was approx. 0.15% at

Fig. 2 e (a) Pores and the surfaces, (b) nitrogen adsorption izoterm and (c) pore size distribution (PSD) curves of the synthesized compound. Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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Fig. 3 e Hydrogen storage capacity of the compound at (a) 77 K and (b) 298 K.

1 bar pressure and 77 K. Hydrogen storage capacities at room temperature (298 K) was calculated and the curves given in Fig. 3b. It is found that the gravimetric total hydrogen percentages decreased extremely to 0.0065 for 1 bar and 0.3007 for 100 bars at 298 K because the vdW interaction gets weaken at higher temperatures. Similarly, excess uptake capacities decreased to 0.2540 and 0.00603 wt.% at 100 bars and 1 bar respectively (Fig. 3b).

Fig. 4 represents the hydrogen molecules which are located inside the crystal structure. The perspective of view could confuse because the positions of the hydrogen molecules. Hence the positions and some selected distances for adsorbed hydrogen molecules given as an orthographic view (Fig. 4). It is determined that the distances are much more than it is seen just because the calculations obey the LJ 12-6 potential and distances.

Fig. 4 e Hydrogen molecule adsorbed structure and the intermolecular distances. Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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As a consequence, it is possible to say that the synthesized compound has good talent at hydrogen storage hence, similar results have been reported previously by researchers. For instance, Park and co-workers [54] reported that MOF structured ZIF-8 coded Zn(MeIM)2 (MeIM: 2-methylimidazolate) with 1.27 wt.% excess hydrogen storage capacity at 77 K and 1 bar. It is very similar to compound that synthesized in this work by the storage capacity but differ with the surface area. The surface area of ZIF-8 reported as 1630 m2/g while the value was 217 m2/g for the MOF synthesized in this work. In another work, Dinca et al. [55] synthesized a cupper based compound with BDT (1,4benzene-ditetrazolate) and calculated surface area as 200 m2/g. However, they found that the mentioned compound could uptake only 0.66 wt.% total hydrogen at 77 K and 1 bar while the present compound could uptake 1.287 wt.% total hydrogen. In essense, surface area is not the measure for the hydrogen storage capacity individually. Storing more hydrogen in small pores was a result of effective interaction between the pore walls and hydrogen molecules. The situation could be explained by the hydrogen-adsorbent interactions which is one of the interaction could affect adsorption. The others were intermolecular (H2eH2) interactions, dispersive forces, electron cloud polarization and quadropole interactions which were described by Reguera [56]. In addition, in the referred works above, ZIF-8 and CuBDT compounds have less electron density in comparison to MOF synthesized in this work. Because the present MOF exist extra electron donor groups on the second ligand 1,10 phenantroline. Finally, it is clear that the 2D MOF synthesized in this work have denser electron cloud and stronger hydrogen-adsorbent interaction which improve the hydrogen storage capacities. Hydrogen and adsorbent interactions, surface characteristics and adsorption energies were simulated to clarify adsorption mechanism deeply. So the isosteric heats which estimate the strength of sorbentesorbate interaction for hydrogen adsorption (Qst) was ~12 kJ/mol for 0.6 wt.% hydrogen adsorption at 77 K. Bae and Snurr [57] investigated the isosteric heats for deliverable amounts of adsorbed hydrogen of some selected MOFs. They reported that the average Qst value for deliverable amounts changes between 23 and 28 kJ/mol. Also, Zhou et al. [58] calculated isosteric heat of hydrogen adsorption of MOF-5 as ~4.8 kJ/mol for 5 wt.% hydrogen at 77 K. Isosteric heats for

3,5-dipyridyl-1,2,4 triazole included MOF structured compounds were ~8 and ~4 kJ/mol for 0.2 wt.% hydrogen storage according to Wei et al. [59]. In another work Villajos et al. [60] reported that Graphene oxide/Nickel decorated MOF-74 hase11.5 kJ/mol for 0.2 wt.% hydrogen storage at 77 K. The results indicate that the synthesized adsorbent has strong adsorption capability in comparison to reported examples. The isosteric heat change for the adsorbed amount of hydrogen plotted in Fig. 5a and the Qst value decreases too little for the higher adsorbed amounts because the type of adsorption isotherm (Fig. 3) show that the pores have already filled by the hydrogen. Adsorbed amount was not increasing too much (Type I isotherm) for higher pressures. Population analysis of the interaction energies for different amountofhydrogeninavacuumslabontheadsorbentsurfaceof synthesizedcompoundhelptoclarifysurfacecharacteristicsof the adsorbent. Fig. 5b shows that the increasing number of hydrogen molecules changes the population for three different adsorption energies regions which represents vacuum slab, adsorbentsurfaceandadsorbentitself.Whenthesmallamount of hydrogen molecules being adsorbed to the adsorbentvacuum slab system, the population slides to the left in the distribution curve. In the other word, lower adsorption energy regions adsorb more hydrogen for the small amount of hydrogen. Mentioned lower adsorption energy (
3.5 to
2.75 kcal/mol) region corresponds to inner sites of the adsorbent. Medium adsorption energy (
2.75 to
2.2 kcal/mol) site and high adsorption energy (
2.2 to 0 kcal/mol) sites corresponds to adsorbent surface and empty spaces (vacuum slab). 500 hydrogen molecule loaded structure of the adsorbent representedandassociatedwithdifferentadsorptionenergyregions/ sites in Fig. 5b. Thus, the positions of the hydrogen molecules inside the adsorbent determined (positions and the views of differentamountofhydrogeninsidetheadsorbentrepresented in SI: Fig. S6).

Conclusion In this work, a novel two dimensional metal organic framework synthesized and characterized experimentally by using

Fig. 5 e (a) Isosteric heat of adsorption change by hydrogen uptake, (b) population analysis of interaction energies for different amount of hydrogen. Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170

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single crystal XRD data, FT-IR and thermal analysis techniques. Then the hydrogen storage ability and surface characteristics of the synthesized compound was determined theoretically by using molecular simulation calculations. It is found that the two dimensional MOF structured novel adsorbent could uptake 1.382 and 1.287 wt.% hydrogen at 77 K, 100 bars and 1 bar respectively. Excess amount of hydrogen that is adsorbed for the same conditions were 1.285 and 1.191 wt.% while the BET surface area was 217 m2/g. In addition, it is found that the compound could uptake hydrogen strongly in internal sites (Qst ¼ ~12 kJ/mol for 0.6 wt.% uptake). Also the surface characteristics, adsorption sites and regions inside were clarified in this work. In conclusion, two dimensional MOF structured compound, synthesized in this work was good at storing hydrogen in comparison to the most known MOFs.

Acknowledgments We would like to thank to Hitit University Scientific Research Project Department for the grant with the project numbers MUH19007.14.002 and MUH19001.14.003.

Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.ijhydene.2016.05.170.

Notes Crystallographic data for the structural analysis has been deposited with the Cambridge Crystallographic Data Centre, CCDC No. 1055199. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: þ44-1223-336033; e-mail: deposit@ ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).

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Please cite this article in press as: Ozturk Z, et al., Novel 2D micro-porous Metal-Organic Framework for hydrogen storage, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.170