Article Cite This: Inorg. Chem. 2018, 57, 13437−13442
pubs.acs.org/IC
Facile Mechanosynthesis of the Archetypal Zn-Based Metal−Organic Frameworks Daniel Prochowicz,†,‡ Jan Nawrocki,† Michał Terlecki,‡ Wojciech Marynowski,† and Janusz Lewinś ki*,†,‡ †
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
‡
Downloaded via UNIV OF LOUISIANA AT LAFAYETTE on November 15, 2018 at 12:51:54 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
S Supporting Information *
ABSTRACT: Mechanochemical methods have been successful in providing rapid access to a number of inorganic−organic functional materials under mild conditions. Recently, we demonstrated a novel mechanochemical strategy for metal− organic framework (MOF) preparation based on predesigned oxo-centered secondary building units. Herein, we develop this method for the facile preparation of the isoreticular MOF (IRMOF) family members based on a combination of an oxozinc amidate cluster, [Zn4(μ4-O)(NHOCPh)6], and selected ditopic aminoterephthalate and 4,4′-biphenyldicarboxylate as well as tritopic 1,3,5-benzenetribenzoate ligands. The resulting IRMOF-3, IRMOF-10, and MOF-177 crystalline materials were characterized using powder X-ray diffraction, IR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis. We found that the character of the organic linker strongly affects the nature of the resulting MOF crystallites after activation processes. The SEM images demonstrate that IRMOF-3 formed microcrystallites in the range of 400−500 nm, while the two other materials exhibited microstructures of amorphous phases. The porosity of each sample was estimated by N2 sorption measurements at 77 K. These results provide an efficient and general method for the mechanosynthesis of Zn-based MOF materials using a predesigned oxozinc cluster.
■
INTRODUCTION Metal−organic frameworks (MOFs) are an emerging class of hybrid inorganic−organic materials that have attracted considerable attention because of their intriguing structural motifs and various potential industrial applications.1−3 With their highly porous and modular nature, MOFs have been examined in the areas of gas storage and separation,4 catalysis,5,6 degradation of harmful agents,7 redox activity,8 and drug-delivery systems.9 Over the last 15 years, a key role in advancing MOF science has been played by classical energyconsuming solvothermal procedures, providing access to a multitude of tailored hybrid inorganic−organic porous materials.10 More recently, a broad set of alternative synthesis methods of MOFs involving electrochemical,11 microwaveand ultrasound-assisted,12,13 and mechanochemical approaches14 have been developed. In particular, the field of mechanochemistry has been thriving in the past decade, as described in a number of excellent reviews.15−19 The solventfree mechanochemical synthesis offers a significant advance by avoiding bulk solvents and high temperatures. Note that the shape, size, and morphology of the MOF materials are very often critical for their various properties and applications.13 Prolonged ball-milling may produce amorphous materials, which can offer exciting opportunities for practical applications in various fields.20,21 In turn, the use of liquid-assisted-grinding (LAG) procedures often facilitates the formation of metal− organic open architectures with improved crystallinity.22−24 The mechanochemical approaches have been successful in © 2018 American Chemical Society
providing rapid access to a number of inorganic−organic functional materials under mild conditions, including molecular cages,25,26 perovskites for solar cells,27−34 and microporous MOFs.35−41 To date, the milling procedures have been developed for the synthesis of several MOF materials, i.e., MIL-100,35 MIL-78,36 MOF-74,37 UiO-based derivatives,38,39 HKUST-1,40 and MOF-5.41 The latter MOF-5 material was synthesized by grinding terephthalic acid and a predesigned oxozinc benzoate42 or amidate41 cluster exhibiting molecular geometries resembling the secondary building unit (SBU) found in Zn-based isoreticular MOFs (IRMOFs).43,44 This so-called “SMART” (SBU-based Mechanochemical Approach for pRecursor Transformation) strategy allows for the first mechanochemical synthesis of the IRMOF structure; however, the applicability of this method for the formation of other IRMOF family members has not yet been demonstrated. Herein, we exploit the use of “SMART” strategy for the synthesis of other prominent examples of IRMOFs composed of octahedral {Zn4O}6+ SBUs and 2-aminoterephthalic acid (IRMOF-3) and 4,4′-biphenyldicarboxylic acid (IRMOF-10). In addition, we utilize this approach to the mechanosynthesis of MOF-177, whose structure is based on {Zn4O}6+ SBUs and triangular 1,3,5-benzenetribenzoate organic linkers. The mechanochemically synthesized MOFs were characterized by Received: July 19, 2018 Published: October 8, 2018 13437
DOI: 10.1021/acs.inorgchem.8b02026 Inorg. Chem. 2018, 57, 13437−13442
Article
Inorganic Chemistry Scheme 1. Illustration of the Mechanochemical “SMART” Strategy Affording Zn-Based MOFs
Figure 1. Comparison of experimental and simulated PXRD patterns for the synthesis of IRMOF-3: (a) benzamide; (b) 2-aminoterephthalic acid; (c) simulated pattern for IRMOF-3 (CSD code EDUSUR); (d) neat grinding reaction of [Zn4(μ4-O)(NHOCPh)6] and 2-aminoterephthalic acid; (e) neat grinding reaction of [Zn4(μ4-O)(NHOCPh)6] and 2-aminoterephthalic acid after activation with THF. Mechanosynthesis of MOF-177. A total of 0.1 g of [Zn4(μ4O)(NHOCPh)6] (0.1 mmol) and 0.0876 g (0.2 mmol) of 1,3,5tris(4-carboxyphenyl)benzene in the presence of 150 μL of N,Ndiethylformamide (DEF) were milled in a 10 mL agate jar for 30 min at 30 Hz. The isolated yield after activation processes was found to be 79%. PXRD. Diffractograms were recorded on an X’Pert MPD PRO (Panalytical) diffractometer equipped with a ceramic tube (Cu anode, λ = 1.54060 Å), a secondary graphite (002) monochromator, and an RTMS X’Celerator (Panalytical) in an angle range of 2θ = 5−40°, by step scanning with a step of 0.02°. Nuclear Magnetic Resonance (NMR). NMR spectra were acquired on a Bruker AVANCE II 300. Complete activation was monitored by 1H NMR [deuterated dimethyl sulfoxide (DMSO-d6), DCl, 25 °C). Because of the low solubility of 4,4′-biphenyldicarboxylic acid in DMSO-d6 and DCl for NMR measurement, we used a NaOD and D2O mixture. Fourier Transform Infrared Attenuated Total Reflectance (FTIRATR) was recorded on a Bruker Tensor apparatus equipped with an ATR accessory. Thermogravimetric Analysis (TGA) Experiments were performed under argon with a heating rate of 2 °C min−1 using a TA Instruments Q600 apparatus. SEM Measurements were performed on a scanning electron microscope (Zeiss ULTRA Plus) with a field-emission gun. Volumetric Gas Sorption studies were undertaken using a Micromeritics Instrument Corp. (Norcross, GA) ASAP 2020 system. Approximately 100−300 mg of the corresponding solid product was transferred to a preweighed sample tube and evacuated under vacuum
IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and N2 adsorption measurements.
■
EXPERIMENTAL SECTION
Syntheses. All reagents were purchased from commercial vendors. Solvents were dried and distilled prior to use. The oxozinc amidate precursor was obtained according to our previously reported procedure.42 The mechanochemical reactions were performed using a Retsch MM400 mixer mill. The reaction vessels were made from agate with two agate balls of 7 mm diameter as grinding media. For each experiment, the product was scraped from the vessel and activated by immersion in anhydrous tetrahydrofuran (THF) or trichloromethane (CHCl3) for 3 days under a N2 atmosphere, during which time the activation solvent was replenished three times. The solvent was further removed under vacuum at 100 °C. The samples after N2 adsorption analysis were characterized by PXRD. Mechanosynthesis of IRMOF-3. A total of 0.1 g of [Zn4(μ4O)(NHOCPh)6] (0.1 mmol) and 0.054 g (0.3 mmol) of 2aminoterephthalic acid were milled in a 10 mL agate jar for 30 min at 30 Hz. The isolated yield after activation processes was found to be 82%. Mechanosynthesis of IRMOF-10. A total of 0.1 g of [Zn4(μ4O)(NHOCPh)6] (0.1 mmol) and 0.072 g (0.3 mmol) of 4,4′biphenyldicarboxylic acid in the presence of 150 μL of N,Ndimethylformamide (DMF) were milled in a 10 mL agate jar for 30 min at 30 Hz. The isolated yield after activation processes was found to be 77%. 13438
DOI: 10.1021/acs.inorgchem.8b02026 Inorg. Chem. 2018, 57, 13437−13442
Article
Inorganic Chemistry
Figure 2. (a) SEM image of the postreaction mixture for a neat grinding reaction of [Zn4(μ4-O)(NHOCPh)6] and 2-aminoterephthalic acid (a) before and (b) after washing with THF. (c) N2 adsorption isotherm on activated IRMOF-3 at 77 K. at 100 °C on the gas adsorption apparatus until the outgas rate was
