Solvent-Dependent Formation of Three New Bi-MetalâOrganic

Subscriber access provided by UNIV OF DURHAM

Article

Solvent dependent formation of three new Bi-MOFs using a tetracarboxylic acid Milan Köppen, Vanessa Meyer, Jonas Ångström, A. Ken Inge, and Norbert Stock Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b00439 • Publication Date (Web): 15 May 2018 Downloaded from http://pubs.acs.org on May 16, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Solvent dependent formation of three new Bi-MOFs using a tetracarboxylic acid Milan Köppen,† Vanessa Meyer,† Jonas Ångström,‡ A. Ken Inge*,‡ and Norbert Stock*,† †

Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth Str. 2, 24118 Kiel (Germany)

‡

Department of Materials and Environmental Chemistry, Stockholm University, Stockholm SE-106 91 (Sweden)

KEYWORDS: metal-organic frameworks, bismuth, synthesis, high-throughput, thermodiffraction, electron diffraction

ABSTRACT: Systematic solvent screening using high-throughput solvothermal syntheses with bismuth nitrate pentahydrate and 1,2,4,5-tertrakis-(4-carboxyphenyl)benzene (H4TCPB) led to three new porous Bi-MOFs [Bi2(H2TCPB)(TCPB)(H2O)2]·xH2O (CAU-31), (NH2(CH3)2)[Bi(TCPB)(H2O)]·xH2O (CAU-32) and [Bi4(O)2(OH)2(H2TCPB) (TCPB)(H2O)2]·xH2O (CAU-33). Compounds CAU-31, -32 and -33 were synthesized in CH3OH, CH3OH/DMF and DMF/toluene, respectively. The crystal structures were determined using electron diffraction and single-crystal X-ray diffraction in combination with the Rietveld method. The structures of CAU-31 and CAU-32 are composed of isolated Bi3+ ions as the inorganic building unit (IBU), which are connected by the linker ions to form a layered structure with inclined interpenetration and a three-dimensional anionic network, respectively. The IBU of CAU-33 consists of infinite bismuthoxo rods forming a three-dimensional network by connection of the organic linkers. For CAU-33 structural flexibility was observed and two phases denoted α- and β-CAU-33 could be isolated.

Introduction

the four reported Bi-MOF structures reveals that NOTT220 is the only one constructed from a finite IBU (binuclear Bi2O14 cluster). The other three Bi-MOF structures are composed of infinite bismuth-oxo rods: linear face sharing BiO9 polyhedra in CAU-7, edge-sharing helical BiO9 polyhedra in CAU-17 and a highly condensed linear chain of BiO7 polyhedra in CAU-35.

Metal-organic frameworks (MOFs) are a class of nanoporous materials that have only been intensely studied for the last two decades.1 Their unique properties open potential applications in the field of gas separation,2 medicine,3 catalysis,4 sensors,5 heat transformation6,7 and many others. Some MOFs exhibit unusually flexible crystalline structures where the pore size and shape change considerably as a response to the surrounding environment.8–10 These breathing MOFs display significant and reversible changes of the cell parameters, without changing the interconnection of the inorganic and organic building units and thus do not influence the framework topology.11

The syntheses of all porous Bi-MOFs have been performed under solvothermal reaction conditions, employing either methanol12,14,15 (CAU-7 and CAU-17), a mixture of DMF and water15 (CAU-35) or a more complex solvent mixture using piperazine, nitric acid, DMF and acetonitrile13 (NOTT-220). Based on these results, methanol and DMF seem to be promising candidates for the synthesis of new Bi-MOFs.

A large number of MOF materials have been discovered and reported with most metals of the periodic table, but among these, there are only four Bi-MOFs exhibiting permanent porosity, as proven by adsorption experiments (CAU-7,12 NOTT-220,13 CAU-17,14 CAU-3515). In contrast to many metal ions, such as Cu2+ and Zr4+, where often the same inorganic building units (IBUs) are observed in numerous MOFs, Bi3+ ions mainly exhibit high coordination numbers (CN = 7-12) and flexible coordination environments in its metal complexes,16–23 which results in mostly unique IBUs and crystal structures. Inspection of

To analyze and understand the properties of a MOF, elucidation of their crystal structures is indispensable. Structure determination of Bi-MOFs by single crystal Xray diffraction (SC-XRD) is often hampered by the fact that usually only small crystals are formed.12 In addition, the compounds frequently crystallize in large unit cells leading to powder X-ray diffraction (PXRD) patterns with a high degree of reflection overlap.14 Also, in diffraction experiments, the patterns are dominated by diffraction on the heavy scatterer Bi. Structure model building is also challenging particularly for Bi-MOFs due to the unpre1

ACS Paragon Plus Environment

Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

dictable nature of the IBU. The coordination spheres around the Bi3+ ions are often distorted by the electron lone pair and thus no regular BiOx polyhedra are observed.

Page 2 of 10

establish the influence of parameters such as molar ratios of starting materials,28 pH,29 reaction temperature30 or combination of these parameters31 on the product formation.

In such problematic cases electron diffraction in combination with Rietveld refinement against PXRD data can be employed.24 Electron diffraction, which can be performed in a transmission electron microscope (TEM), provides the opportunity to collect single crystal diffraction data on crystals with diameters on the nanoscale.12,25 However, this technique poses severe challenges to the experimentalist due to beam damage issues. Recently the applicability of the technique has been enhanced due to considerable improvements in sample protection environments and detector technology. New detectors permit electron diffraction data acquisition while continuously rotating the crystalline sample in the electron beam. This also reduces data acquisition time from approximately one hour to a few minutes or less and thus effectively reduces beam damage considerably.25 Continuous rotation electron diffraction26 recently led to the elucidation of the crystal structure of the commercial drug bismuth subgallate, which has been used in medicine for over a century. The electron diffraction data set was collected in only three minutes.25 In this work, we present three new Bi-MOFs (CAU-31, CAU-32, CAU-33) synthesized with 1,2,4,5-tertrakis-(4carboxyphenyl)benzene (H4TCPB, Fig. 1) as the organic building unit. The discovery of the new phases was achieved by systematically varying the solvent of the reaction mixture. Several diffraction techniques and their combinations were used to solve and refine the new crystal structures.

Results and discussion In the search of new porous Bi-MOFs the structure and synthesis conditions of previously described materials can be used for inspiration. Thus infinite bismuth-oxo rods as IBUs seem to be well suited in combination with large rigid organic linker molecules such as H3BTB (1,3,5benzene-tribenzoic acid) or H3TATB (triazine-2,4,6-triyltribenzoic acid). This lead to the formation of a honeycomb-like structures in CAU-7 ([Bi(BTB)]12) and CAU-7TATB ([Bi(TATB)]15) as well as in CAU-35 ([Bi2(O)(OH)(TATB)]·H2O15). This connectivity is schematically shown in Fig. 1. By extending this approach to the connection of infinite bismuth-oxo rods by rigid tetracarboxylate ions, two different structures can be easily anticipated. In one model each rod is connected to eight others, while in the other a connection to six rods is accomplished. The different connectivities should result in pores of different diameters. In order to confirm our hypothesis a high-throughput (HT) investigation using the rigid tetracarboxylic acid H4TCPB was carried out. The HT methodology is well suited for the in depth study of complex parameter systems.27 Its efficiency has been demonstrated in order to

Fig. 1: Schematic illustrations of the previously described interconnection of bismuth-oxo rods by tricarboxylate ions as observed in CAU-7-TATB and CAU-35 (top) and possible interconnections of infinite bismuth-oxo rods (purple) by 4rigid tetracarboxylate molecules, such as the TCPB linker (bottom).

HT Synthesis In the current HT investigation the role of solvent on the product formation in the system Bi3+ / H4TCPB / solvent has been studied employing CH3OH and DMF. These two solvents have been previous successfully used for the synthesis of porous Bi-MOFs.12,14,15 By varying synthesis parameters (solvent, temperature, concentration, molar ratios, additives, etc.) three new Bi-MOFs were discovered (Fig. 2). The synthesis conditions are summarized in Tab. S1. Reactions were carried out at four different temperatures (80, 100, 120 and 140 °C) using molar ratios of linker to metal of 1:1 and 1:2. These parameters have little influence on the product formation. Changing the solvent from pure CH3OH to mixtures of CH3OH and DMF or pure DMF the compounds [Bi2(TCPB)(H2TCPB)(H2O)]·xH2O (CAU-31), (NH2(CH3)2)[Bi(TCPB)(H2O)]·xH2O (CAU-32) and [Bi4(O)2(OH)2(H2TCPB)(TCPB)(H2O)2]·xH2O (CAU-33) 2


Page 3 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 2: Summary of the results of the high-throughput investigations using Bi(NO3)3·5 H2O and H4TCPB in different molar ratios and varying the solvent employed. Reactions were carried out at four different temperatures. Results are based on the PXRD measurements of the reaction products.

suggests structural flexibility. More information is provided in the SI and in the discussion of the chemical stability.

are obtained. CAU-33 was first discovered employing pure DMF as the solvent, but addition of small amounts of toluene (10 %) to the reaction mixture results in a higher product yield. Phase purity, crystallinity and yield of CAU-31, -32 and -33 were optimized by varying reaction temperature, molar ratios of linker to metal and the concentration of the starting materials. These optimized reaction conditions are given in the experimental section. Phase purity was confirmed by PXRD measurements (Fig. S3, S9 and S15).

Crystal structures To determine the crystal structures of CAU-31, CAU-32 and CAU-33, various crystallographic techniques were applied. The structure of CAU-32 was solved and refined from SC-XRD, while the structures of CAU-31 and CAU-33 were refined with Rietveld methods against PXRD data after obtaining a starting model from continuous rotation electron diffraction data or SC-XRD data respectively. Detailed descriptions of the determination and the crystal structures including also figures of the connection and coordination of the Bi3+ ions are provided in the SI. Crystallographic data are summarized in Table 1 and Tables S2-S5.

For CAU-33, two slightly different PXRD patterns were observed after synthesis (denoted α- and β-CAU-33). In most cases phase mixtures were obtained directly after the synthesis, but upon storage under ambient conditions for one day, the α-form transforms into the β-form, which

Table 1. Summarized crystallographic information of CAU-31, CAU-32 and CAU-33 (more details in Tab. S2-S5). CAU-31

CAU-32

structure solution

electron diffraction

SC-XRD

structure refinement

Rietveld

SC-XRD

Le Bail

Rietveld

space group

P21/c

P21/n

C2/c

C2/c

a

11.5261(5) Å

11.188(1) Å

32.785(4) Å

33.001(2) Å

b

28.265(2) Å

24.552(2) Å

23.011(4) Å

22.909(2) Å

c

11.575(2) Å

16.315(2) Å

10.139(2) Å

10.435(1) Å

α

90°

90

90°

90°

β

104.647(7)°

91.365(3)°

110.74(1)°

99.53(1)°

γ

90°

volume

3648.4(5) Å

α-CAU-33

β-CAU-33 SC-XRD

90

90° 3

90°

3

4480.1(8) Å

Rwp = 8.64 %

R1 = 0.0716

Rwp = 11.39 %

Rwp = 4.29 %

GoF = 3.81

wR2 = 0.1328

GoF = 1.76

GoF = 6.47

7153.63 Å

3

7779.9(2) Å

3

3



Page 4 of 10

Fig. 3: a) A single layer in [Bi2(TCPB)(H2TCPB)(H2O)]·xH2O (CAU-31). Bismuth cations are represented as purple BiO8 polyhe4dra. b) The augmented 2D bex net. Bismuth cations are represented as 3-connected triangles in purple, TCPB as 4-connected 2rectangles in green and 2-connected H2TCPB as edges between two triangles.

Crystal structure of CAU-31 Crystals of [Bi2(TCPB)(H2TCPB)(H2O)]·xH2O (CAU-31) were needle-shaped and had an approximate thickness of 700 nm (Fig. S1). While the small size made conventional SC-XRD impractical, they were thin enough for electron diffraction. Therefore, continuous rotation electron diffraction datasets were collected from a number of crystals and the structure of CAU-31 was solved from one of the datasets in the space group P21/c (Fig. S2). Subsequently, Rietveld refinement was performed against PXRD data due to the high R-values from the electron diffraction data caused by dynamical scattering. The results are listed in Tab. S2 and the final Rietveld plot is shown in Fig. S3. The framework is composed of Bi3+ ions chelated by three carboxylate groups and a layered structure is formed (Fig. 3a). The coordination sphere of the Bi3+ ions is completed by H2O molecules. One of the two unique TCPB linkers in the asymmetric unit is four-connected (TCPB4-) while the other is two-connected (H2TCPB2-). In the underlying 2D net the IBUs are represented as three-connected nodes, TCPB4- as four-connected nodes, and two-connected H2TCPB2- are represented as edges decorating the bex net with transitivity 2 2 and the point symbol {4.62}2{42.62.82} (Fig 3b).32,33 The 2D layers exhibit inclined interpenetration resulting in a 3D interlocked structure (Fig. 4a and 4b). Inclined interpenetration of 2D layers (i.e. interlocking layers that are inclined rather than parallel to one another) in coordination polymers is rather uncommon.34,35 The H2TCPB2- linkers from one layer pass through rings formed by two Bi3+ and two four-connected TCPB4- in the inclined interpenetrated layer. Crystal structure of CAU-32 Due to the sufficiently large size of the crystals (Fig. S1), the structure of (NH2(CH3)2)[Bi(TCPB)(H2O)]·xH2O (CAU-32, Fig. 5a) was solved and refined from SC-XRD data. The crystal structure of CAU-32 is composed of Bi3+ ions chelated by four carboxylate groups and one H2O molecule resulting in an anionic 3D framework structure. Each TCPB4- linker also connects to four Bi3+ ions. Charge

balance is achieved by dimethyl ammonium ions, which are formed by hydrolysis of DMF during synthesis. The asymmetric unit comprises one Bi3+ and two TCPB4- ions, which are represented as a tetrahedron and two unique rectangles in the augmented net, respectively (Fig. 5b).

Fig. 4: a) Two inclined interlocking layers in CAU-31 shown in blue and gold viewed approximately perpendicular to the 2layers. H2TCPB ions of the blue layer pass through rings in the gold layer. b) Inclined interlocking of layers viewed parallel to the layers. Blue layers interlock with gold layers but not other blue layers, and vice versa.

4


Page 5 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 5: a) Crystal structure of (NH2(CH3)2)[Bi(TCPB)(H2O)]·xH2O (CAU-32). BiO9 polyhedra are depicted in purple, while all other non-hydrogen atoms are represented as spheres, viewed along [100]. b) The underlying augmented net of CAU-32 with the 4IBU represented as purple tetrahedra and the organic four-connected TCPB linkers as green rectangles. c) The 3D channel system of CAU-32 shown in yellow, viewed along [001].

The underlying trinodal net has transitivity 3 4 and the point symbol {4.85}2{42.82.102}{86}.32,33 CAU-32 exhibits a 3D channel system (Fig. 5c and video in SI) with a diameter of approximately 4.4 Å taking the van der Waals radii of the framework atoms into account. The positions of guest species in the pores, could not be determined through inspection of the Fourier difference map due to positional disorder, however the presence of dimethyl ammonium cations was confirmed by 1H-NMR spectroscopy (Fig. S28). Crystal structure of CAU-33 The crystal structure of [Bi4(O)2(OH)2(H2TCPB)(TCPB) (H2O)2]·xH2O (CAU-33) was solved from single crystal Xray diffraction data. However, due to the small crystal size (approximately 30 µm, Fig. S1), reflections had low intensities overall. While the data quality was far from ideal, the positions of the bismuth ions as well as the approximate positions of the TCPB-linker molecules could be determined from the data set. Structure refinement was therefore performed against powder X-ray diffraction data. The results are listed in Tab. S4 and the final Rietveld plot is shown in Fig. 6. The IBUs of CAU-33 are corner-sharing bismuth-oxo rods that extend along the caxis. The rods are linked by the H2TCPB2- and TCPB4- ions resulting in a 3D framework structure (Fig. 7a). The crystal structure comprises two crystallographically unique Bi3+ cations as well as two TCPB linkers which are both centered around inversion centers. The two unique Bi3+ cations have a rather low coordination number of five, irregular coordination geometries most likely due to the stereochemically active electron lone pair and are linked through μ-OH and μ3-O bridging oxygen atoms in the rods. Charge balance is achieved through the bridging oxygen, hydroxide and partially deprotonated carboxylate groups. Similar to CAU-31, one of the two TCPB-linkers is four connected and bridges four rods, while the other is

two-connected and bridges two rods through two carboxylate groups that are diagonally across the molecule. Thus, two crystallographically independent 1D lozengeshaped channels along the c-axis parallel to the rods are formed. The diameters of the channels are 9.5×4.6 Å and 4.4×4.1 Å taking the van der Waals radii of framework atoms into account (Fig. 7a). A topological representation of the structure was established using the points of extension (carboxylate carbon atoms) and the branch points on the central aromatic ring as nodes as is recommended for rod-based MOFs by O’Keeffe.36

Fig. 6: Rietveld plot of the refinement of β-CAU-33. Experimental and theoretical PXRD pattern shown as black and red line, respectively. The difference is drawn in blue, while the positions of reflections are indicated by black bars.

5



Page 6 of 10

Fig. 7: a) Crystal structure of CAU-33 viewed along [001]. Bismuth, carbon and oxygen atoms are depicted in purple, grey and red, respectively. b) The underlying augmented net of CAU-33 viewed along [001] and c) [100]. The IBUs are represented as pur42ple rods, the four-connected TCPB linkers as green rectangles, and two-connected H2TCPB linkers as edges.

The resulting underlying net is trinodal with transitivity 3 5 and the point symbol {34.42}{34.43.52.6.82.92.10}2{4.82}2 (Fig. 7b and 7c).32,33 The inorganic rods in the net are simplified to trans edge-sharing square pyramids where the opposite edges of the base of the square pyramid are shared. The pinnacle of neighboring square pyramids that share edges along the rod point in opposite directions. The rods are interconnected directly by edges (twoconnected H2TCPB2-) and through rectangles (fourconnected TCPB4-). The structure of CAU-33 resembles one of the two possible connections mentioned in Fig. 1, which describes the connection of an infinite rod to eight other rods. Stability To determine the thermal stability of CAU-31, -32 and -33, thermogravimetric (TG) analyses were performed on all three samples up to a temperature of 700 °C (Fig. 8c and more detailed in Fig. S17-S19). The TG data shows that H2O/CH3OH molecules are removed up to a temperature of 110 °C in all three MOFs. The characterized sample of CAU-33 contained residues of DMF from the synthesis, which were removed up to 260 °C. Decomposition

of the linker molecules were observed from ~350 °C (CAU-31 and -32) and ~400 °C (CAU-33) in the TG measurements. CAU-32 and -33 were additionally characterized by heating the samples in an open capillary while collecting PXRD data (Fig. 8a and 8b). At 125 °C a phase transition is observed for CAU-32, which can be correlated with the loss of solvent molecules from the pores as observed by TG analysis. However, the PXRD pattern of this phase could not be indexed and thus the structure could not be determined. The crystallinity of CAU-32 decreases at around 275 °C, which is presumably related to the decomposition of the [NH2(CH3)2]+ ions. For CAU-33 a higher thermal stability was observed, as it only decomposes in a region of 360-450 °C, which correlates with the TG analysis data. To investigate the chemical stability of the three new Bi-MOFs, each of the compounds was stirred in different aqueous solutions (pH 1-13) and in other solvents for 24 h. The samples were afterwards filtered off, washed with methanol and characterized by PXRD (Fig. S29-S37).

Fig. 8: a,b) Results of the temperature-dependent PXRD experiments with CAU-32 and β–CAU-33, respectively. c) Results of the thermogravimetric analyses of CAU-31, -32 and -33.

6


Page 7 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CAU-31 appears to be stable in most organic solvents and in water between pH 3-11. Surprisingly, acetone, DMF and tetrahydrofuran altered the crystal structure as observed by PXRD, and thus are no suitable media for CAU31. Analyzing the chemical stability experiments performed with CAU-32 was rather challenging. Due to its structural changes, PXRD patterns differ significantly (Fig. 8a and Fig. S16). No other than the as-synthesized phase could be characterized structurally. CAU-32 seems to be stable in all tested organic solvents. In aqueous solutions the crystal structure slowly degrades, indicated by increasing background in the PXRD measurements, caused by X-ray amorphous products. As mentioned before, CAU-33 exhibits structural flexibility and two different PXRD patterns are observed (denoted α- and β-phase) depending the on the presence of guest molecules in the pores. The PXRD patterns are shown in Fig. 9, as both phases are obtained either phase pure or as mixtures after synthesis.

Fig. 9: Measured PXRD patterns of α-CAU-33 (bottom) and β-CAU-33 (top) and a mixture of both (middle) as they always appear after synthesis, before they transform into the βphase.

We were able to determine and refine the unit cell parameters of the α-phase, which transforms quickly into the β-phase when being stored under ambient conditions or by thermal treatment at 60 °C. The cell parameters of both phases are somewhat similar (space group C2/c), but the unit cell volume of the β-phase is 9% larger than the α-phase (Tab. 1, Tab. S4-S5). However, by performing stability tests on β-CAU-33, we found that a transition between the α- and the β-phase can be induced by stirring the MOF in different solvents. Ethanol, DMF, acetone, DMSO, ethyl acetate, tetrahydrofuran and water between pH 3-11 led to the α-phase, whereas acetonitrile, nheptane, toluene and dichloromethane kept the material

in the β-phase. CAU-33 is stable in all listed solvents and additionally in water between pH 3-11. Gas sorption Sorption experiments with CAU-31, -32 and -33 were carried out upon activation of the samples at elevated temperatures under reduced pressure and confirmed their porosity (more details are provided in Fig. S20-S24). N2 sorption isotherms were recorded at 77 K. Whereas CAU31 and -32 showed no N2 uptake, a type I(a) isotherm was observed for CAU-33. The BET surface area was determined to be aBET = 450 m2/g and the micropore volume to be Vmic = 0.21 cm3/g. Additionally, we carried out H2O sorption experiments on CAU-31 and -32 at 298 K, which revealed an uptake of 15.0 and 5.5 mol(H2O)/mol, respectively.

Conclusion Variation of solvents in the chemical system Bi3+/TCPB4/CH3OH/DMF led to the discovery of three new Bi-MOFs, which were characterized in detail (denoted CAU-31, CAU-32 and CAU-33). A high-throughput investigation allowed the optimization of the synthesis parameters of all three compounds in terms of phase purity, crystallinity and yield. Two of the crystal structures were solved from SC-XRD, while continuous rotation electron diffraction was used to solve the third structure. All three presented compounds exhibit rather unique structural features for Bi-MOFs including the first example of inclined interlocking layers in CAU-31, and the first example of a flexible crystal structure in CAU-33. The chemical stability of CAU-31, -32 and-33 in solvents was investigated by stirring the MOFs for 24 h in various solvents. Water stability was observed for CAU-31 and CAU-33 in a range of pH 3-11. All three MOFs were stable in most other tested solvents. These experiments provide insight into how likely these compounds can be used in potential applications such as drug delivery, as well as how the loading of the MOFs can be accomplished. For CAU-33 high thermal stability was observed.

Experimental The chemicals were purchased from Aldrich, Alfa Aesar or Walter CMP and used without further purification. Syntheses were carried out under solvothermal conditions in a custom-made high-throughput multiclave with 2 mL PTFE liners.27 PXRD measurements were carried out with CuKα1 radiation on a Stoe Stadi P Combi diffractometer in transmission geometry, equipped with a MYTHEN detector. Temperature-dependent PXRD was performed in a Stoe capillary furnace in an open 0.5 mm quartz capillary. The Rietveld refinements of CAU-31 and -33 were performed in TOPAS Academic 6.37 Structure determination of all three novel phases were performed by ShelXT.38 Sorption measurements were performed with a BEL Japan, Inc. BELSORP-max. The speciﬁc surface area of CAU-33 was determined using the Rouquerol approach.39 The micropore volume of CAU-33 was calculated at p/p0 = 7



0.5. Thermogravimetric measurements were performed on a NETZSCH STA-409CD under air ﬂow of 75 ml/min with a heating rate of 4 K/min. IR spectra were measured on a Bruker ALPHA-P spectrometer using an ATR unit. l H-NMR spectroscopy was measured on a Bruker DRX 500 spectrometer. Scanning electron microscopy was performed on a Philips ESEM XL 30. Optimized synthesis of [Bi2(H2TCPB)(TCPB)(H2O)2] ·xH2O (CAU-31): To a mixture of H4TCPB (5 mg, 8.95 µmol) and ground Bi(NO3)3·5H2O (4.3 mg, 8.95 µmol) in a 2 mL PTFE liner, 1 mL CH3OH was added. The sealed reactor was shaken for 10 min and heated in an oven to 80 °C over 1 h and kept at this temperature for 12 h. After cooling over 1 h to room temperature, the solid product was filtered off and washed with CH3OH. A white powder was obtained in a yield of 5.5 mg. The reaction was repeated several times, to obtain a suitable amount for detailed characterization. Phase purity was confirmed by PXRD (Fig. S3) and elemental analysis (calculated (%) for [Bi2(O8C34H20)(O8C34H18)(H2O)2]·15.5H2O: C 44.3 H 4.0; measured (%): C 44.2 H 3.6). Optimized synthesis of (NH2(CH3)2)[Bi(TCPB)(H2O)] ·xH2O (CAU-32): To a mixture of H4TCPB (10 mg, 17.9 µmol) and ground Bi(NO3)3·5H2O (8.7 mg, 17.9 µmol) in a 2 mL PTFE liner, 800 µL CH3OH and 200 µL DMF were added. The sealed reactor was shaken for 10 min and heated in an oven to 100 °C over 1 h and kept at this temperature for 12 h. After cooling over 1 h to room temperature, the solid product was filtered off and washed with CH3OH. A white powder was obtained in a yield of 15.3 mg. The reaction was repeated several times, to obtain a suitable amount for detailed characterization. Phase purity was confirmed by PXRD (Fig. S15) and elemental analysis (calculated (%) for (NH2(CH3)2)[Bi(O8C34H18) (H2O)]·4H2O: C 48.1 H 4.0 N 1.6; measured (%): C 48.5 H 3.8 N 1.2). Optimized synthesis of [Bi4(O)2(OH)2(H2TCPB)(TCPB) (H2O)2]·xH2O (β-CAU-33): To a mixture of H4TCPB (10 mg, 17.9 µmol) and ground Bi(NO3)3·5H2O (17.4 mg, 35.8 µmol) in a 2 mL PTFE liner, 450µL DMF and 50 µL toluene were added. The sealed reactor was shaken for 10 min and heated in an oven to 120 °C over 1 h and kept at this temperature for 12 h. After cooling over 1 h to room temperature, the solid product was filtered off. The product was afterwards stirred in a 1:1 mixture of CH3OH/DMF at 100 °C for 10 min, washed with CH3OH and dried at 60 °C for 1 h. A white powder was obtained in a yield of 13.7 mg. The reaction was repeated several times, to obtain a suitable amount for detailed characterization. Phase purity was confirmed by PXRD (Fig. S9) and elemental analysis (calculated (%) for [Bi4(O)2(OH)2(O8C34H20)(O8C34H18) (H2O)2]·7H2O·DMF: C 37.9 H 2.9 N 0.6; measured (%): C 37.9 H 2.7 N 0.7). Crystal structure determination of (H2N(CH3)2)[Bi(TCPB)(H2O)] (CAU-32 (as)): Single crystal X-ray diffraction data were collected on a Bruker APEX-II CCD at 295 K (λ = 0. 71073 Å). Structure determi-

Page 8 of 10

nation was performed in ShelXT.38 Atoms were refined using a full-matrix least squares technique on F2 in ShelXL.40 All non-hydrogen atoms were refined with anisotropic displacement parameters. A riding model was used to constrain the coordinates of hydrogen atoms bonded to parent carbon atoms.

ASSOCIATED CONTENT Crystallographic, PXRD, TGA, NMR and IR data, as well as a video of the crystal structure of CAU-32. CIF-files of CAU-31, CAU-32, CAU-33. This material is available free of charge via the Internet at http://pubs.acs.org. Crystallographic information files (CIFs) are deposited in CCDC database as CCDC 1821217 (CAU-31), CCDC 1821218 (CAU-32) and CCDC 1821219 (CAU-33).

AUTHOR INFORMATION Corresponding Author * correspondence to [email protected] and [email protected].

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Funding Sources Any funds used to support the research of the manuscript should be placed here (per journal style).

Notes Any additional relevant notes should be placed here.

ACKNOWLEDGMENT We thank Helge Reinsch and Dirk Lenzen for helpful discussions. AKI is supported by the Swedish Foundation for Strategic Research (SSF) and also a scholarship from the Knut and Alice Wallenberg Foundation (KAW).

REFERENCES (1) Moghadam, P. Z.; Li, A.; Wiggin, S. B.; Tao, A.; Maloney, A. G. P.; Wood, P. A.; Ward, S. C.; Fairen-Jimenez, D. Development of a Cambridge Structural Database Subset: A Collection of Metal–Organic Frameworks for Past, Present, and Future. Chem. Mater. 2017, 29, 2618–2625. (2) Li, J.-R.; Sculley, J.; Zhou, H.-C. Metal-organic frameworks for separations. Chem. Rev. 2012, 112, 869–932. (3) Orellana-Tavra, C.; Marshall, R. J.; Baxter, E. F.; Lázaro, I. A.; Tao, A.; Cheetham, A. K.; Forgan, R. S.; Fairen-Jimenez, D. Drug delivery and controlled release from biocompatible metal– organic frameworks using mechanical amorphization. J. Mater. Chem. B 2016, 4, 7697–7707. (4) Zhu, L.; Liu, X.-Q.; Jiang, H.-L.; Sun, L.-B. Metal-Organic Frameworks for Heterogeneous Basic Catalysis. Chem. Rev. 2017, 117, 8129–8176. (5) Kreno, L. E.; Leong, K.; Farha, O. K.; Allendorf, M.; van Duyne, R. P.; Hupp, J. T. Metal-organic framework materials as chemical sensors. Chem. Rev. 2012, 112, 1105–1125. (6) Lenzen, D.; Bendix, P.; Reinsch, H.; Fröhlich, D.; Kummer, H.; Möllers, M.; Hügenell, P. P. C.; Gläser, R.; Henninger, S.;

8


Page 9 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Stock, N. Scalable Green Synthesis and Full-Scale Test of the Metal-Organic Framework CAU-10-H for Use in AdsorptionDriven Chillers. Adv. Mater. 2018, 30, 1705869. (7) Lange, M. F. de; Verouden, K. J. F. M.; Vlugt, T. J. H.; Gascon, J.; Kapteijn, F. Adsorption-Driven Heat Pumps: The Potential of Metal-Organic Frameworks. Chem. Rev. 2015, 115, 12205– 12250. (8) Loiseau, T.; Serre, C.; Huguenard, C.; Fink, G.; Taulelle, F.; Henry, M.; Bataille, T.; Férey, G. A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration. Chem. - Eur. J. 2004, 10, 1373–1382. (9) Ferey, G. Swelling Hybrid Solids. Z. anorg. allg. Chem. 2012, 638, 1897–1909. (10) Niekiel, F.; Ackermann, M.; Guerrier, P.; Rothkirch, A.; Stock, N. Aluminum-1,4-cyclohexanedicarboxylates: Highthroughput and temperature-dependent in situ EDXRD studies. Inorg. Chem. 2013, 52, 8699–8705. (11) Kitagawa, S.; Kitaura, R.; Noro, S.-i. Functional porous coordination polymers. Angew. Chem., Int. Ed. 2004, 43, 2334– 2375. (12) Feyand, M.; Mugnaioli, E.; Vermoortele, F.; Bueken, B.; Dieterich, J. M.; Reimer, T.; Kolb, U.; de Vos, D.; Stock, N. Automated Diffraction Tomography for the Structure Elucidation of Twinned, Sub-micrometer Crystals of a Highly Porous, Catalytically Active Bismuth Metal-Organic Framework. Angew. Chem. Int. Ed. 2012, 124, 10373–10376. (13) Savage, M.; Yang, S.; Suyetin, M.; Bichoutskaia, E.; Lewis, W.; Blake, A. J.; Barnett, S. A.; Schröder, M. A novel bismuthbased metal-organic framework for high volumetric methane and carbon dioxide adsorption. Chem. - Eur. J. 2014, 20, 8024– 8029. (14) Inge, A. K.; Köppen, M.; Su, J.; Feyand, M.; Xu, H.; Zou, X.; O'Keeffe, M.; Stock, N. Unprecedented Topological Complexity in a Metal-Organic Framework Constructed from Simple Building Units. J. Am. Chem. Soc. 2016, 138, 1970–1976. (15) Köppen, M.; Beyer, O.; Wuttke, S.; Lüning, U.; Stock, N. Synthesis, functionalisation and post-synthetic modification of bismuth metal-organic frameworks. Dalton Trans. 2017, 46, 8658–8663. (16) Burrows, A. D.; Jurcic, M.; Mahon, M. F.; Pierrat, S.; Roffe, G. W.; Windle, H. J.; Spencer, J. Bismuth coordination networks containing deferiprone: Synthesis, characterisation, stability and antibacterial activity. Dalton Trans. 2015, 44, 13814–13817. (17) Busch, S.; Stein, I.; Ruschewitz, U. Hydrate Isomerism in Coordination Polymers of Bismuth and Acetylenedicarboxylate. Z. anorg. allg. Chem. 2012, 638, 2098–2101. (18) Chen, X.; Cao, Y.; Zhang, H.; Chen, Y.; Chen, X.; Chai, X. Hydrothermal synthesis and characteristics of 3-D hydrated bismuth oxalate coordination polymers with open-channel structure. J. Solid State Chem. 2008, 181, 1133–1140. (19) Deibert, B. J.; Velasco, E.; Liu, W.; Teat, S. J.; Lustig, W. P.; Li, J. High-Performance Blue-Excitable Yellow Phosphor Obtained from an Activated Solvochromic Bismuth-Fluorophore Metal–Organic Framework. Cryst. Growth Des. 2016, 16, 4178– 4182. (20) Kan, L.; Li, J.; Luo, X.; Li, G.; Liu, Y. Three novel bismuthbased coordination polymers: Synthesis, structure and luminescent properties. Inorg. Chem. Commun. 2017, 85, 70–73. (21) Thirumurugan, A.; Cheetham, A. K. Anionic MetalOrganic Frameworks of Bismuth Benzenedicarboxylates: Synthesis, Structure and Ligand-Sensitized Photoluminescence. Eur. J. Inorg. Chem. 2010, 2010, 3823–3828. (22) Wang, G.; Liu, Y.; Huang, B.; Qin, X.; Zhang, X.; Dai, Y. A novel metal-organic framework based on bismuth and trimesic

acid: Synthesis, structure and properties. Dalton Trans. 2015, 44, 16238–16241. (23) Feyand, M.; Köppen, M.; Friedrichs, G.; Stock, N. Bismuth tri- and tetraarylcarboxylates: Crystal structures, in situ X-ray diffraction, intermediates and luminescence. Chem. - Eur. J. 2013, 19, 12537–12546. (24) Wan, W.; Sun, J.; Su, J.; Hovmöller, S.; Zou, X. Threedimensional rotation electron diffraction: Software RED for automated data collection and data processing. J. Appl. Crystallogr. 2013, 46, 1863–1873. (25) Wang, Y.; Takki, S.; Cheung, O.; Xu, H.; Wan, W.; Öhrström, L.; Inge, A. K. Elucidation of the elusive structure and formula of the active pharmaceutical ingredient bismuth subgallate by continuous rotation electron diffraction. Chem. Commun. 2017, 53, 7018–7021. (26) Gemmi, M.; La Placa, M. G. I.; Galanis, A. S.; Rauch, E. F.; Nicolopoulos, S. Fast electron diffraction tomography. J. Appl. Crystallogr. 2015, 48, 718–727. (27) Stock, N. High-throughput investigations employing solvothermal syntheses. Microporous Mesoporous Mater. 2010, 129, 287–295. (28) Hermer, N.; Reinsch, H.; Mayer, P.; Stock, N. Synthesis and characterisation of the porous zinc phosphonate [Zn 2 (H 2 PPB)(H 2 O) 2 ]·xH 2 O. CrystEngComm 2016, 18, 8147–8150. (29) Stock, N.; Bein, T. High-throughput synthesis of phosphonate-based inorganic-organic hybrid compounds under hydrothermal conditions. Angew. Chem., Int. Ed. 2004, 43, 749– 752. (30) Bauer, S.; Stock, N. Implementation of a temperaturegradient reactor system for high-throughput investigation of phosphonate-based inorganic-organic hybrid compounds. Angew. Chem., Int. Ed. 2007, 46, 6857–6860. (31) Sonnauer, A.; Stock, N. Complex Hydrothermal Reaction Systems: A Systematic Investigation of Copper Phosphonatoethanesulfonates by High-Throughput Methods. Eur. J. Inorg. Chem. 2008, 2008, 5038–5045. (32) Delgado-Friedrichs, O.; O'Keeffe, M. Identification of and symmetry computation for crystal nets. Acta Crystallogr., Sect. A: Found. Crystallogr. 2003, 59, 351–360. (33) Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological Analysis of Crystal Structures with the Program Package ToposPro. Cryst. Growth Des. 2014, 14, 3576–3586. (34) Gómez-Lor, B.; Gutiérrez-Puebla, E.; Iglesias, M.; Monge, M. A.; Ruiz-Valero, C.; Snejko, N. Novel 2D and 3D Indium Metal-Organic Frameworks: Topology and Catalytic Properties †. Chem. Mater. 2005, 17, 2568–2573. (35) Jiang, H.-L.; Makal, T. A.; Zhou, H.-C. Interpenetration control in metal–organic frameworks for functional applications. Coord. Chem. Rev. 2013, 257, 2232–2249. (36) Schoedel, A.; Li, M.; Li, D.; O'Keeffe, M.; Yaghi, O. M. Structures of Metal-Organic Frameworks with Rod Secondary Building Units. Chem. Rev. 2016, 116, 12466–12535. (37) A. Coelho. TOPAS Academic 6; Coelho Software, 2016. (38) Sheldrick, G. M. SHELXT - integrated space-group and crystal-structure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71, 3–8. (39) Rouquerol, J.; Llewellyn, P.; Rouquerol, F. Is the bet equation applicable to microporous adsorbents? Stud. Surf. Sci. Catal. 2007, 160, 49–56. (40) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112–122.

9



Page 10 of 10

For Table of Contents Use Only

Solvent dependent formation of three new Bi-MOFs using a tetracarboxylic acid Milan Köppen, Vanessa Meyer, Jonas Ångström, A. Ken Inge and Norbert Stock

Systematic solvent screening using high-throughput solvothermal syntheses led to the three new porous Bi-MOFs CAU-31, CAU-32 and CAU-33. The crystal structures were determined using electron diffraction and single-crystal X-ray diffraction in combination with the Rietveld method. CAU-31 is composed of inclined interpenetrating layers and for CAU-33 structural flexibility was observed.

10


Solvent-Dependent Formation of Three New Bi-MetalâOrganic

Recommend Documents

Solvent-Dependent Formation of Three New Bi-MetalâOrganic