characterization of the mof by powder x-ray diffraction (pxrd) and nuclear magnetic resonance (nmr) after digestion

三唑和四唑官能化 Zr-MOF 的合成和表征

Metal-organic frameworks (MOFs) are three-dimensional porous materials that are formed through coordination bonds between metal clusters and multi-topic organic ligands. MOFs have garnered significant attention due to their permanent porosity, low density, and ability to associate organic and inorganic components, which enables diverse applications1,2. Moreover, the vast range of metal nodes and strut organic linkers offer MOFs theoretically unlimited structural combinations. Even with identical framework structures, MOFs&#39; physical and chemical properties can be modified through ligand functionalization with chemical tags. This modification process offers a promising route to tailor the properties of MOFs for specific applications3,4,5,6,7,8,9.
Both the pre-functionalization of ligands prior to MOF synthesis and post-synthetic modification (PSM) of MOFs have been employed to introduce and/or modify functional groups in MOF ligands10,11. In particular, covalent PSMs have been extensively studied to introduce new functional groups and generate a range of MOFs with diverse functionalities12,13,14. For instance, UiO-66-NH2 can be converted to amide-functionalized UiO-66-AMs with different chain lengths (ranging from the shortest acetamide to the longest n-hexyl amide) through acylation reactions with appropriate acyl halides (such as acetyl chloride or n-hexanoyl chloride)15,16. This approach demonstrates the versatility of covalent PSMs to introduce specific functional groups onto MOF ligands, paving the way for a broad range of applications.
In addition to covalent PSMs, post-synthetic ligand exchange (PSE) is a promising strategy for modifying MOFs (Figure 1). Since MOFs are composed of coordination bonds between metals and ligands (such as carboxylates), these coordination bonds can be replaced with external ligands from a solution. Exposing MOFs to a solution containing the desired ligand with chemical tags can be incorporated into the MOFs via PSE17,18,19,20,21,22. Since the PSE process is accelerated by the existence of coordinative solvents, the phenomenon is also called solvent-assisted ligand exchange (SALE)23,24. This approach offers a flexible and facile method for functionalizing MOFs with a wide range of external ligands, enabling a broad spectrum of applications25,26,27,28,29.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65619/65619fig01.jpg" /> 
Figure 1: Synthesis of triazole and tetrazole-functionalized H2BDC ligands and preparation of triazole- and tetrazole-functionalized UiO-66 MOF through PSE. <a href="https://www.jove.com/files/ftp_upload/65619/65619fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The progress of the PSE process can be controlled by adjusting the ligand ratio, exchange temperature, and time. Notably, room temperature PSE can be employed to obtain functionalized MOFs by exchanging ligands from a solution into MOF solids20. The PSE strategy is particularly useful for introducing both thermally unstable functional groups (such as azido groups) and coordinative functional groups (such as phenol groups) into MOF structures18. In addition, the PSE strategy has been applied to various MOFs with metal and coordination bond variations. This exchange is a universal process in the chemistry of MOFs30,31,32. In this study, we present a detailed protocol for PSE to obtain functionalized MOFs from pristine, non-functionalized MOFs, and we provide a characterization strategy to confirm successful functionalization of the MOFs. This method demonstrates the versatility and convenience of PSE for modifying MOFs with diverse functional groups.
Tetrazole-containing benzene-1,4-dicarboxylic acid (H2BDC-Tetrazole)33, and triazole-containing benzene-1,4-dicarboxylic acid (H2BDC-Triazole) are synthesized as target ligands and utilized in the PSE of UiO-66 MOFs to obtain novel, coordination-free, triazole-containing MOFs. Both triazoles and tetrazoles possess acidic N-H protons on their heterocyclic rings and can coordinate with metal cations, thus enabling their use in constructing MOFs34,35. However, there are limited studies on incorporating coordination-free tetrazoles and triazoles into MOFs and related structures. In case of triazole-functionalized Zr-MOFs, UiO-68 type MOFs were investigated to photophysical properties through direct solvothermal synthesis with benzotriazole functionalities36. For tetrazole-functionalized Zr-MOFs, the mixed direct synthesis was employed33. These heterocycle-functionalized MOFs could provide potential coordinating sites in MOF pores for catalysis, selective molecular uptake by binding affinity, and energy-related applications, such as proton conduction in fuel cells.

作者聚焦：金属有机框架功能化：合成后配体交换的进步、挑战和力量 

通过合成后配体交换合成三唑和四唑功能化Zr基金属有机骨架

Our main research topic is functionalizing the porous metal-organic frameworks, MOFs, with interesting functional groups through various techniques. This study is focused on heterocycle installation in MOFs. PSE, post-synthetic ligand exchange is the main technique in this work.The ligand with target functional group could be installed in presynthesized MOFS throughout the solid-solution exchange process. Especially, some of the unstable ligands and ligands with coordinating groups could be efficiently incorporated into MOFs through the PSE techniques. Both triazole and tetrazole functional groups have multiple coordinating nitrogen grooves.Therefore, there is competition for coordination between metal carboxylate and metal triazolate or tetrazolate. The incorporation ratio of target ligands is easily controlled in the PSE process and multiple targets could be installed in a single MOF through this approach.

Watch this Scientific Journal Video about Characterization of the MOF by Powder X-Ray Diffraction PXRD and Nuclear Magnetic Resonance NMR After Digestion at JoVE.com

Characterization of the MOF by Powder X-Ray Diffraction (PXRD) and Nuclear Magnetic Resonance (NMR) After Digestion  

通过粉末X射线衍射（PXRD）和核磁共振（NMR）在消化后表征MOF

将与UiO-66-Triazole交换的约10mgMOF固体转移到粉末X射线衍射样品架中。将样品架放入衍射仪中，收集粉末X射线衍射图。要开始核磁共振表征，请将约30毫克交换的MOF固体转移到新鲜的4毫升小瓶中。然后使用微量移液器将 400 微升 DMSO-d6 移至 MOF 样品中。使用微量移液管将200微升4.14摩尔氟化铵氧化氘溶液转移到MOF粉末的DMSO-d6悬浮液中。超声处理非均相混合物30分钟，直到MOF在消化后溶解在二甲基亚砜氧化氘混合溶剂中。完成后，通过聚偏二氟乙烯注射器过滤器过滤溶液，同时将其从四毫升小瓶转移到核磁共振管中，从而去除任何剩余的不溶性固体。为了确定交换的成功，测量了粉末X射线衍射图，并与原始UiO-66 MOF的结晶度进行了比较。交换的UiO-66-三唑和UiO-66-四氮唑在粉末X射线衍射图中的反射峰位置、相对强度和宽度与原始UiO-66 MOFs相匹配，表明配体交换不影响框架结构。通过比较非功能化BDC和BDC-三唑或BDC-四唑的整合来确定交换比率。合成后配体交换分析发现三唑和四唑的交换比例分别为33%和30%。

characterization-mof-powder-x-ray-diffraction-pxrd-nuclear-magnetic

Research

JoVE Journal

Chemistry

Characterization of the MOF by Powder X-Ray Diffraction (PXRD) and Nuclear Magnetic Resonance (NMR) After Digestion

383 次观看.  Chungbuk National University. 将与UiO-66-Triazole交换的约10mgMOF固体转移到粉末X射线衍射样品架中。将样品架放入衍射仪中，收集粉末X射线衍射图。要开始核磁共振表征，请将约30毫克交换的MOF固体转移到新鲜的4毫升小瓶中。然后使用微量移液器将 400 微升 DMSO-d6 移至 MOF 样品中。使用微量移液管将200微升4.14摩尔氟化铵氧化氘溶液转移到MOF粉末的DMSO-d6悬浮液中。超声处理非均相混合物30分钟，直到MOF?...

视频: Characterization of the MOF by Powder X-Ray Diffraction (PXRD) and Nuclear Magnetic Resonance (NMR) After Digestion  

Synthesis of Triazole and Tetrazole-Functionalized Zr-Based Metal-Organic Frameworks Through Post-Synthetic Ligand Exchange

Metal-organic frameworks (MOFs) are a class of porous materials that are formed through coordination bonds between metal clusters and organic ligands. Given their coordinative nature, the organic ligands and strut framework can be readily removed from the MOF and/or exchanged with other coordinative molecules. By introducing target ligands to MOF-containing solutions, functionalized MOFs can be obtained with new chemical tags via a process called post-synthetic ligand exchange (PSE). PSE is a straightforward and practical approach that enables the preparation of a wide range of MOFs with new chemical tags via a solid-solution equilibrium process. Furthermore, PSE can be performed at room temperature, allowing the incorporation of thermally unstable ligands into MOFs. In this work, we demonstrate the practicality of PSE by using heterocyclic triazole- and tetrazole-containing ligands to functionalize a Zr-based MOF (UiO-66; UiO = University of Oslo). After digestion, the functionalized MOFs are characterized via various techniques, including powder X-ray diffraction and nuclear magnetic resonance spectroscopy.

Post-synthetic ligand exchange (PSE) is a versatile and powerful tool for installing functional groups into metal-organic frameworks (MOFs). Exposing MOFs to solutions containing triazole- and tetrazole-functionalized ligands can incorporate these heterocyclic moieties into Zr-MOFs through PSE processes.

Metal-organic frameworks (MOFs) are a class of porous materials that are formed through coordination bonds between metal clusters and organic ligands. ...

科研

化学

Setting up the Post-synthetic Ligand Exchange (PSE) Process, Exchanged MOF Isolation and Washing Process

Begin by measuring 23.3 milligrams of H2BDC triazole and place it into the scintillation vial. To dissolve the H2BDC ligand in the aqueous solution, transfer 1.0 milliliters of the 4%potassium hydroxide solution into the vial using a glass pipette. Next, sonicate the mixture until all solids completely dissolve.Add one molar hydrochloric acid solution into the decarboxylate-containing vial and stir until a pH of 7 is reached. Add 33 milligrams of UiO-66 MOF to the scintillation vial. Then incubate the vial with the MOF and ligand at room temperature and 120 RPM in a shaker for 24 hours.Next, isolate the solid MOF from the mixture by centrifugation at 1166g for five minutes. at room temperature. Add 10 milliliters of fresh methanol to the obtained solid MOF and shake the vial, creating a heterogeneous mixture to dissolve any remaining unchanged BDC ligands.Isolate the solid once again by centrifuging the mixture at 1166g for five minutes at room temperature and dry it.

建立合成后配体交换（PSE）过程，交换MOF分离和洗涤过程

Transfer approximately 10 milligrams of the MOF solid exchanged with UiO-66-Triazole to a powder X-ray diffraction sample holder. Place the sample holder in the diffractometer, and collect the powder X-ray diffraction pattern. To begin NMR characterization, transfer around 30 milligrams of the exchanged MOF solid to a fresh four milliliter vial.Then move 400 microliters of DMSO-d6 to the MOF sample using a micro pipette. Transfer 200 microliters of 4.14 molar ammonium fluoride deuterium oxide solution to a DMSO-d6 suspension of MOF powder using a micro pipette. Sonicate the heterogeneous mixture for 30 minutes until the MOF is dissolved in the dimethyl sulfoxide deuterium oxide mixed solvent after digestion.Once done, remove any remaining insoluble solids by filtering the solution through a polyvinylidene difluoride syringe filter while transferring it from the four milliliter vial to a nuclear magnetic resonance tube. To determine the success of the exchange, powder X-ray diffraction patterns were measured and compared to pristine UiO-66 MOF for crystallinity. The position of reflection peaks, relative intensity, and broadness in the powder X-ray diffraction patterns of exchanged UiO-66-Triazole and UiO-66-Tetrazole matched with pristine UiO-66 MOFs, indicating that the ligand exchange did not impact the framework structure.The exchange ratios were determined by comparing the integration of nonfunctionalized BDC and BDC-Triazole or BDC-Tetrazole. The exchange ratios for Triazole and Tetrazole were found to be 33%and 30%respectively from post synthetic ligand exchange analysis.