MOFs@Top J：2022.04.17-2022.04.23

Confinement of Luminescent Guests in Metal–Organic Frameworks: Understanding Pathways from Synthesis and Multimodal Characterization to Potential Applications of LG@MOF Systems

Chemical Reviews， Pub Date : 2022-04-15 , 

DOI: 10.1021/acs.chemrev.1c00980
Mario Gutiérrez, Yang Zhang, Jin-Chong Tan

This review gives an authoritative, critical, and accessible overview of an emergent class of fluorescent materials termed “LG@MOF”, engineered from the nanoscale confinement of luminescent guests (LG) in a metal–organic framework (MOF) host, realizing a myriad of unconventional materials with fascinating photophysical and photochemical properties. We begin by summarizing the synthetic methodologies and design guidelines for representative LG@MOF systems, where the major types of fluorescent guest encompass organic dyes, metal ions, metal complexes, metal nanoclusters, quantum dots, and hybrid perovskites. Subsequently, we discuss the methods for characterizing the resultant guest–host structures, guest loading, photophysical properties, and review local-scale techniques recently employed to elucidate guest positions. A special emphasis is paid to the pros and cons of the various methods in the context of LG@MOF. In the following section, we provide a brief tutorial on the basic guest–host phenomena, focusing on the excited state events and nanoscale confinement effects underpinning the exceptional behavior of LG@MOF systems. The review finally culminates in the most striking applications of LG@MOF materials, particularly the “turn-on” type fluorochromic chemo- and mechano-sensors, noninvasive thermometry and optical pH sensors, electroluminescence, and innovative security devices. This review offers a comprehensive coverage of general interest to the multidisciplinary materials community to stimulate frontier research in the vibrant sector of light-emitting MOF composite systems.

https://pubs.acs.org/doi/abs/10.1021/acs.chemrev.1c00980

Freestanding Metal–Organic Frameworks and Their Derivatives: An Emerging Platform for Electrochemical Energy Storage and Conversion

Chemical Reviews， Pub Date : 2022-04-21 , 

DOI: 10.1021/acs.chemrev.1c00978
Bing He, Qichong Zhang, Zhenghui Pan, Lei Li, Chaowei Li, Ying Ling, Zhixun Wang, Mengxiao Chen, Zhe Wang, Yagang Yao, Qingwen Li, Litao Sun, John Wang, Lei Wei

Metal–organic frameworks (MOFs) have recently emerged as ideal electrode materials and precursors for electrochemical energy storage and conversion (EESC) owing to their large specific surface areas, highly tunable porosities, abundant active sites, and diversified choices of metal nodes and organic linkers. Both MOF-based and MOF-derived materials in powder form have been widely investigated in relation to their synthesis methods, structure and morphology controls, and performance advantages in targeted applications. However, to engage them for energy applications, both binders and additives would be required to form postprocessed electrodes, fundamentally eliminating some of the active sites and thus degrading the superior effects of the MOF-based/derived materials. The advancement of freestanding electrodes provides a new promising platform for MOF-based/derived materials in EESC thanks to their apparent merits, including fast electron/charge transmission and seamless contact between active materials and current collectors. Benefiting from the synergistic effect of freestanding structures and MOF-based/derived materials, outstanding electrochemical performance in EESC can be achieved, stimulating the increasing enthusiasm in recent years. This review provides a timely and comprehensive overview on the structural features and fabrication techniques of freestanding MOF-based/derived electrodes. Then, the latest advances in freestanding MOF-based/derived electrodes are summarized from electrochemical energy storage devices to electrocatalysis. Finally, insights into the currently faced challenges and further perspectives on these feasible solutions of freestanding MOF-based/derived electrodes for EESC are discussed, aiming at providing a new set of guidance to promote their further development in scale-up production and commercial applications.

https://pubs.acs.org/doi/abs/10.1021/acs.chemrev.1c00978

Adenine-incorporated metal–organic frameworks

Coordination Chemistry Reviews， Pub Date : 2022-04-22 ,

DOI: 10.1016/j.ccr.2022.214558
Rakesh Kumar Gupta, Muhammad Riaz, Mo Ashafaq, Zhi-Yong Gao, Rajender S. Varma, Da-Cheng Li, Ping Cui, Chen-Ho Tung, Di Sun

Metal-organic frameworks (MOFs) endowed with unique structural features, namely permanent porosity, high surface area, tunable pore size, and potential applications in diverse domains, have garnered immense attention in recent decades. The availability of large numbers of organic linkers, metal nodes, and multiple synthetic tactics has broadened the scope of MOF research wherein the judicial selection of building blocks, and especially the organic linker is critical for the task-specific MOF design. The adenine nucleobase is an ideal choice among the broadly available organic linkers because of its small size, being nitrogen-riched and non-toxic, and its ready availability comprising multiple Lewis basic coordination sites and modes. In addition, adenine with its amino group (–NH2) can network through non-covalent interfaces (host and guest) rather than covalent interactions, i.e., hydrogen bonding via Watson-Crick (N1, N6H) and Hoogsteen (N7, N6H) face contact, thus making ensued adenine-based MOF materials more appealing. Herein, we appraise the general introduction of syntheses and design strategies, the structural influence of adenine incorporation to the ensued attributes of MOFs, and their applications in diverse research fields such as gas storage (selective adsorption of CO2), separation, luminescence, drug delivery, catalysis, and sensing.

https://www.sciencedirect.com/science/article/pii/S0010854522001539

Porphyrin and phthalocyanine based covalent organic frameworks for electrocatalysis

Coordination Chemistry Reviews， Pub Date : 2022-04-22 ,

DOI: 10.1016/j.ccr.2022.214563
Shengsheng Huang, Kai Chen, Ting-Ting Li

Covalent organic frameworks (COFs) are a burgeoning class of crystalline porous polymers. Owing to their unique features including tunable porosity, abundant accessible active sites, synthetically controllability, and pre-designed topological structures, COFs have been widely employed in various fields including catalysis, energy storage and conversion, gas adsorption, and optoelectronics. The incorporation of porphyrin (Por-) and phthalocyanine (Pc-) building units into COFs endows COFs with unique structural characteristics, excellent optical and electrical properties. Recent years have witnessed significant progress in reasonable design and construction of Por- and Pc-based COFs for electrocatalytic water splitting, CO2 reduction, and oxygen reduction. Herein, the synthetic strategies of Por- and Pc-based COFs are first summarized, which includes the rational design of building units and linkers, and the reaction types used in constructing Por- and Pc-based COFs. A systematic overview of the application of Por- and Pc-based COFs in the electrocatalytic reactions including CO2 reduction reaction (CO2RR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are then performed. Lastly, the current challenges and directions to tailor Por- and Pc-based COFs for efficient and stable electrocatalysis are presented.

https://www.sciencedirect.com/science/article/pii/S0010854522001588

Toward azo-linked covalent organic frameworks by developing linkage chemistry via linker exchange

Nature Communications， Pub Date : 2022-04-21 ,

DOI: 10.1038/s41467-022-29814-3
Zhi-Bei Zhou, Peng-Ju Tian, Jin Yao, Ya Lu, Qiao-Yan Qi, Xin Zhao

Exploring new linkage chemistry for covalent organic frameworks (COFs) provides a strong driving force to promote the development of this emerging class of crystalline porous organic materials. Herein we report a strategy to synthesize COFs with azo linkage, one of the most important functional unit in materials science but having not yet been exploited as a linkage of COFs. This strategy is developed on the basis of in situ linker exchange, by which imine-linked COFs are completely transformed into azo-linked COFs (Azo-COFs). Moreover, distinct properties of Azo-COFs from their corresponding imine-linked precursors are observed, indicating unique property of Azo-COFs. This strategy provides a useful approach to develop new linkage chemistry for COFs. It also has established a synthetic method for azo-linked COFs, which not only enriches the family of COFs but also offers a platform to explore properties and applications of this class of crystalline porous conjugated polymers.

https://www.nature.com/articles/s41467-022-29814-3

Multivariate analysis of disorder in metal–organic frameworks

Nature Communications， Pub Date : 2022-04-21 ,

DOI: 10.1038/s41467-022-29849-6
Adam F. Sapnik, Irene Bechis, Alice M. Bumstead, Timothy Johnson, Philip A. Chater, David A. Keen, Kim E. Jelfs, Thomas D. Bennett

The rational design of disordered frameworks is an appealing route to target functional materials. However, intentional realisation of such materials relies on our ability to readily characterise and quantify structural disorder. Here, we use multivariate analysis of pair distribution functions to fingerprint and quantify the disorder within a series of compositionally identical metal–organic frameworks, possessing different crystalline, disordered, and amorphous structures. We find this approach can provide powerful insight into the kinetics and mechanism of structural collapse that links these materials. Our methodology is also extended to a very different system, namely the melting of a zeolitic imidazolate framework, to demonstrate the potential generality of this approach across many areas of disordered structural chemistry.

https://www.nature.com/articles/s41467-022-29849-6

Multi-stimuli-engendered radical-anionic MOFs: Visualization of structural transformation upon radical formation

Chem， Pub Date : 2022-04-20 , 

DOI: 10.1016/j.chempr.2022.03.023
Seonghun Park, Juhyung Lee, Hwakyeung Jeong, Sangeun Bae, Joongoo Kang, Dohyun Moon, Jinhee Park

Understanding the dynamic structural changes accompanying radical formation provides detailed insights into the design of stimuli-responsive redox-active materials. In this study, we develop a metal-organic framework (MOF) comprising a π-acidic 1,4,5,8-naphthalenediimide (NDI)-based ligand and Nd3+, viz. X-DGIST-4 (X = synthesis temperature in °C, DGIST = Daegu Gyeongbuk Institute of Science and Technology). The reduction of the NDI moieties to the radical-anionic state (NDI·−) in 75-DGIST-4 can be triggered by various stimuli (heat, X-rays, and ultraviolet, visible, and infrared light), indicating the presence of structure-guided multiple electron transfer pathways. The single-crystal-to-single-crystal transformation of 75-DGIST-4 upon X-ray-induced radical formation reveals sequential structural changes. The solvothermally synthesized radical-anionic MOF, viz. 150-DGIST-4, offers a more complete structural understanding of the radical-anionic state. Importantly, the stabilization of radical-anionic NDI·− by adjacent benzoates allows this state to be visualized by single-crystal X-ray diffractometry; the pendant benzoate is twisted to optimize the electrostatic interaction between NDI·− and the benzoate phenyl group.

https://www.sciencedirect.com/science/article/pii/S2451929422001607

Installation of synergistic binding sites onto porous organic polymers for efficient removal of perfluorooctanoic acid

Nature Communications，Pub Date : 2022-04-19 ,

DOI: 10.1038/s41467-022-29816-1
Xiongli Liu, Changjia Zhu, Jun Yin, Jixin Li, Zhiyuan Zhang, Jinli Li, Feng Shui, Zifeng You, Zhan Shi, Baiyan Li, Xian-He Bu, Ayman Nafady, Shengqian Ma

Herein, we report a strategy to construct highly efficient perfluorooctanoic acid (PFOA) adsorbents by installing synergistic electrostatic/hydrophobic sites onto porous organic polymers (POPs). The constructed model material of PAF-1-NDMB (NDMB = N,N-dimethyl-butylamine) demonstrates an exceptionally high PFOA uptake capacity over 2000 mg g−1, which is 14.8 times enhancement compared with its parent material of PAF-1. And it is 32.0 and 24.1 times higher than benchmark materials of DFB-CDP (β-cyclodextrin (β-CD)-based polymer network) and activated carbon under the same conditions. Furthermore, PAF-1-NDMB exhibits the highest k2 value of 24,000 g mg−1 h−1 among all reported PFOA sorbents. And it can remove 99.99% PFOA from 1000 ppb to <70 ppt within 2 min, which is lower than the advisory level of Environmental Protection Agency of United States. This work thus not only provides a generic approach for constructing PFOA adsorbents, but also develops POPs as a platform for PFOA capture.

https://www.nature.com/articles/s41467-022-29816-1

Defects engineering simultaneously enhances activity and recyclability of MOFs in selective hydrogenation of biomass

Nature Communications， Pub Date : 2022-04-19 , 

DOI: 10.1038/s41467-022-29736-0
Wenlong Xu, Yuwei Zhang, Junjun Wang, Yixiu Xu, Li Bian, Qiang Ju, Yuemin Wang, Zhenlan Fang

The development of synthetic methodologies towards enhanced performance in biomass conversion is desirable due to the growing energy demand. Here we design two types of Ru impregnated MIL-100-Cr defect engineered metal-organic frameworks (Ru@DEMOFs) by incorporating defective ligands (DLs), aiming at highly efficient catalysts for biomass hydrogenation. Our results show that Ru@DEMOFs simultaneously exhibit boosted recyclability, selectivity and activity with the turnover frequency being about 10 times higher than the reported values of polymer supported Ru towards D-glucose hydrogenation. This work provides in-depth insights into (i) the evolution of various defects in the cationic framework upon DLs incorporation and Ru impregnation, (ii) the special effect of each type of defects on the electron density of Ru nanoparticles and activation of reactants, and (iii) the respective role of defects, confined Ru particles and metal single active sites in the catalytic performance of Ru@DEMOFs for D-glucose selective hydrogenation as well as their synergistic catalytic mechanism.

https://www.nature.com/articles/s41467-022-29736-0

Achieving gas pressure-dependent luminescence from an AIEgen-based metal-organic framework

Nature Communications， Pub Date : 2022-04-19 , 

DOI: 10.1038/s41467-022-29737-z
Zhijia Li, Feilong Jiang, Muxin Yu, Shengchang Li, Lian Chen, Maochun Hong

Materials exhibiting aggregation-induced emission (AIE) behaviour enable strong emission in solid state and can respond to various external stimuli, which may facilitate the development of materials for optical sensing, bioimaging or optoelectronic devices. Herein, we use an AIE luminogen 2’,5’-diphenyl-[1,1’:4’,1”-terphenyl]-4,4”-dicarboxylic acid as the ligand to prepare an AIEgen-based MOF (metal-organic framework) named FJI-H31. FJI-H31 exhibits bright luminescence under ambient conditions (under air and at room temperature), but almost no emission is observed under vacuum. Our investigation shows that the emission intensity displays a smooth and reversible enhancement with increased gas pressure, which may be attributed to the restriction of intramolecular motion brought by structural deformation under pressure stimulus. Unlike most pressure-responsive MOFs, the luminescence reverts to its original state once gas pressure recovers. By virtue of its unique optical properties, a luminescent MOF with sensing ability of gas-pressure is realized.

https://www.nature.com/articles/s41467-022-29737-z

Dual Metalation in a Two-Dimensional Covalent Organic Framework for Photocatalytic C–N Cross-Coupling Reactions
Journal of the American Chemical Society, Pub Date : 2022-04-21 ,

DOI: 10.1021/jacs.2c01814
Ayan Jati, Kaushik Dey, Maryam Nurhuda, Matthew A. Addicoat, Rahul Banerjee, Biplab Maji

Covalent organic frameworks (COFs) are promising hosts in heterogeneous catalysis. Herein, we report a dual metalation strategy in a single two-dimensional-COF TpBpy for performing a variety of C–N cross-coupling reactions. [Ir(ppy)2(CH3CN)2]PF6 [ppy = 2-phenylpyridine], containing two labile CH3CN groups, and NiCl2 are used as iridium and nickel-metal precursors, respectively, for postsynthetic decoration of the TpBpy COF. Moving from the traditional approach, we focus on the COF-backbone host for visible-light-mediated nickel-catalyzed C–N coupling reactions. The controlled metalation and recyclability without deactivation of both catalytic centers are unique with respect to previously reported coupling strategies. We performed various photoluminescence, electrochemical, kinetic, and Hammett correlation studies to understand the salient features of the catalyst and reaction mechanism. Furthermore, theoretical calculations delineated the feasibility of electron transfer from the Ir center to the Ni center inside the confined pore of the TpBpy COF. The dual metal anchoring within the COF backbone prevented nickel-black formation. The developed protocol enables selective and reproducible coupling of a diverse range of amines (aryl, heteroaryl, and alkyl), carbamides, and sulfonamides with electron-rich, neutral, and poor (hetero) aryl iodides up to 94% isolated yield. The reaction can also be performed on a gram scale. Furthermore, to establish the practical implementation of this approach, we have applied the synthetic strategy for the late-stage diversification of the derivatives of ibuprofen, naproxen, gemfibrozil, helional, and amino acids. The methodology could also be applied to synthesize pharmacophore N,5-diphenyloxazol-2-amine and Food and Drug Administration-approved drugs, including flufenamic acid, flibanserin, and tripelennamine.

https://pubs.acs.org/doi/abs/10.1021/jacs.2c01814