Visible light-induced photocatalysis is a promising way for environmental remediation due to efficient utilization of solar energy. Recently, metal-organic frameworks (MOFs) have attracted increasing ...attention in the field of photocatalysis. In comparison with traditional metal oxide semiconductors, MOFs have many advantages, such as high specific surface area, rich topology and easily tunable porous structure. In this review, we aim to summarize and illustrate recent advances in MOF-based photocatalysis for environmental remediation under visible light, including wastewater treatment, air purification and disinfection. A series of strategies have been designed to modify and regulate pristine MOFs for enhanced photocatalytic performance, such as ligand functionalization, mixed-metal/linker strategy, metal ion/ligand immobilization, dye sensitization, metal nanoparticle loading, carbon material decoration, semiconductor coupling, MOF/COF coupling, carrier loading and magnetic recycling. The above modifications may result in extended visible light absorption, efficient generation, separation and transfer of photogenerated charges, as well as good recyclability. However, there are still many challenges and obstacles. In order to meet the requirements of using MOF photocatalysis as a friendly and stable technology for low-cost practical applications, its future development prospects are also discussed.
Highly photoactive MOFs can be engineered
via
various strategies for the purpose of extended visible light absorption, more efficient generation, separation and transfer of charge carriers, as well as good recyclability.
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
, 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 k
value of 24,000 g mg
h
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.
Connecting molecular building blocks by covalent bonds to form extended crystalline structures has caused a sharp upsurge in the field of porous materials, especially covalent organic frameworks ...(COFs), thereby translating the accuracy, precision, and versatility of covalent chemistry from discrete molecules to two-dimensional and three-dimensional crystalline structures. COFs are crystalline porous frameworks prepared by a bottom-up approach from predesigned symmetric units with well-defined structural properties such as a high surface area, distinct pores, cavities, channels, thermal and chemical stability, structural flexibility and functional design. Due to the tedious and sometimes impossible introduction of certain functionalities into COFs
via de novo
synthesis, pore surface engineering through judicious functionalization with a range of substituents under ambient or harsh conditions using the principle of coordination chemistry, chemical conversion, and building block exchange is of profound importance. In this review, we aim to summarize dynamic covalent chemistry and framework linkage in the context of design features, different methods and perspectives of pore surface engineering along with their versatile roles in a plethora of applications such as biomedical, gas storage and separation, catalysis, sensing, energy storage and environmental remediation.
This review article summarizes the recent progress in the pore surface engineering of covalent organic frameworks (COFs) for various applications.
Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such ...as C2H2/CO2. Herein, we propose a new type of ultra‐strong C2H2 nano‐trap based on multiple binding interactions to efficiently capture C2H2 molecules and separate C2H2/CO2 mixture. The ultra‐strong acetylene nano‐trap shows a benchmark Qst of 79.1 kJ mol−1 for C2H2, a record high pure C2H2 uptake of 2.54 mmol g−1 at 1×10−2 bar, and the highest C2H2/CO2 selectivity (53.6), making it as a new benchmark material for the capture of C2H2 and the separation of C2H2/CO2. The locations of C2H2 molecules within the MOF‐based nanotrap have been visualized by the in situ single‐crystal X‐ray diffraction studies, which also identify the multiple binding sites accountable for the strong interactions with C2H2.
A new type of ultra‐strong C2H2 nano‐trap featuring the synergistic effect of multiple open metal sites has been proposed for separating C2H2/CO2 mixture gas. The unique C2H2 nano‐trap shows the strongest binding interaction with C2H2 and a benchmark for C2H2/CO2 separation. The binding mechanism for C2H2 was studied through single‐crystal X‐ray diffraction experiments and molecular simulation studies.
Industrial synthesis is driven by a delicate balance of the value of the product against the cost of production. Catalysts are often employed to ensure product turnover is economically favorable by ...ensuring energy use is minimized. One method, which is gaining attention, involves cooperative catalytic systems. By inserting a flexible polymer into a metal–organic framework (MOF) host, the advantages of both components work synergistically to create a composite that efficiently fixes carbon dioxide to transform various epoxides into cyclic carbonates. The resulting material retains high yields under mild conditions with full reusability. By quantitatively studying the kinetic rates, the activation energy was calculated, for a physical mixture of the catalyst components to be about 50 % higher than that of the composite. Through the unification of two catalytically active components, a new opportunity opens up for the development of synergistic systems in multiple applications.
More than the sum of its parts: Two catalytically active components, a metal–organic framework (MOF) host and an ionic polymer, are combined into a single material. They synergistically work together lowering the energy barrier of a reaction, further than a mixture of the individual components. This process is demonstrated by the fixation of carbon dioxide with epoxides, forming industrially relevant cyclic carbonates.
Herein, we show how the spatial environment in the functional pores of covalent organic frameworks (COFs) can be manipulated in order to exert control in catalysis. The underlying mechanism of this ...strategy relies on the placement of linear polymers in the pore channels that are anchored with catalytic species, analogous to outer‐sphere residue cooperativity within the active sites of enzymes. This approach benefits from the flexibility and enriched concentration of the functional moieties on the linear polymers, enabling the desired reaction environment in close proximity to the active sites, thereby impacting the reaction outcomes. Specifically, in the representative dehydration of fructose to produce 5‐hydroxymethylfurfural, dramatic activity and selectivity improvements have been achieved for the active center of sulfonic acid groups in COFs after encapsulation of polymeric solvent analogues 1‐methyl‐2‐pyrrolidinone and ionic liquid.
Creating a solvation environment: The catalytic performance of sulfonic acid groups in covalent organic frameworks (COFs) can be greatly amplified by the introduction of polymeric solvent analogues, which create desired solvation environments through hydrogen‐bonding interactions. Improved activity and selectivity was demonstrated by the COF‐catalyzed dehydration of fructose to produce 5‐hydroxymethylfurfural.
Ensuring food security in developing countries is highly challenging due to low productivity of the agriculture sector, degradation of natural resources, high post farming losses, less or no value ...addition, and high population growth. Researchers are striving to adopt newer technologies to enhance supply to narrow the food demand gap. Nanotechnology is one of the promising technologies that could improve agricultural productivity via nano fertilizers, use of efficient herbicides and pesticides, soil feature regulation, wastewater management, and pathogen detection. It is equally beneficial for industrial food processing with enhanced food production with excellent market value, elevated nutritional and sensing property, improved safety, and better antimicrobial protection. Nanotechnology can also reduce post-farming losses by increasing the shelf life with the aid of nanoparticles. However, further investigation is required to solve the safety and health risks associated with the technology.
Agriculture; Food processing; Food security; Nanotechnology; Nanosensors.
Computational exploration has been carried out on three p-tertbutylthiacalix4arene derivatives, namely cone (a), partial-cone (b), and 1,3-alternate (c). These three compounds are recently ...synthesized in high yields (80, 95, and 85%, respectively) and characterized by our group, which showed high uptake efficacy of alkali, heavy, and transition metal ions via liquid–liquid extraction. Significantly, these compounds exhibited high uptake capacity for Cu(II) (74.9 %) and Pb(II) (80.0%) upon using cone (a), and partial-cone (b), respectively.
In this study, in order to optimize how the thiacalix4arene (as a nucleophilic) interacts with the metal ion (as an electrophile), DFT calculations were undertaken. Theoretical IR and UV–Vis spectral features of the titled compounds were computed and compared with their experimental values. Chemical reactivity was ranked based on selected electronic chemical descriptors. Moreover, the active sites of the three compounds were determined by molecular electrostatic potential (MEP) maps. Furthermore, non-linear optical (NLO) properties were investigated and compared with urea as reference material. The results of NLO characteristics showed that the subject compounds are excellent candidates as NLO materials. The enhancement of NLO properties can be qualitatively explained by means of high charge transfer pattern.
Herein, a dynamic spacer installation (DSI) strategy has been implemented to construct a series of multifunctional metal—organic frameworks (MOFs), LIFM‐61/31/62/63, with optimized pore space and ...pore environment for ethane/ethylene separation. In this respect, a series of linear dicarboxylic acids were deliberately installed in the prototype MOF, LIFM‐28, leading to a dramatically increased pore volume (from 0.41 to 0.82 cm3 g−1) and reduced pore size (from 11.1×11.1 Å2 to 5.6×5.6 Å2). The increased pore volume endows the multifunctional MOFs with much higher ethane adsorption capacity, especially for LIFM‐63 (4.8 mmol g−1), representing nearly three times as much ethane as the prototypical counterpart (1.7 mmol g−1) at 273 K and 1 bar. Meanwhile, the reduced pore size imparts enhanced ethane/ethylene selectivity of the multifunctional MOFs. Theoretical calculations and dynamic breakthrough experiments confirm that the DSI is a promising approach for the rational design of multifunctional MOFs for this challenging task.
A dynamic spacer installation (DSI) strategy has been developed to realize a series of multifunctional metal—organic frameworks (MOFs) with optimized pore space and pore environment for ethane/ethylene separation. The installation of functional spacers into the proto‐LIFM‐28 not only improves the pore volume, but also reduces the pore size, leading to enhanced C2H6/C2H4 separation performance.
•A review of the electro- and photochemical synthesis of a variety of transition metal-TCNQ coordination polymers is presented.•Electrochemistry of TCNQ derivatives of coordination polymers based on ...Cu, Ag, Mn, Fe, Co, Ni, Zn and Cd is discussed.•Future outlook of this research area and application of these materials is discussed.
TCNQ− radical anions (TCNQ=7,7,8,8,-tetracyanoquinodimethane) form a wide range of semiconducting coordination polymers when coordinated to transition metals. Some materials such as CuTCNQ and AgTCNQ exhibit molecular switching and memory storage properties; others have intriguing magnetic properties and for example may behave as molecular magnets at low temperature. In this review, the electro- and photo-chemical synthesis and characterization of this important class of material is reviewed. In particular, the electrochemistry and the redox properties of TCNQ derivatives of coordination polymers based on Cu, Ag, Mn, Fe, Co, Ni, Zn and Cd transition metals are surveyed, with an emphasis on the mechanistic aspects of their electrochemical formation via nucleation-growth processes. Given that TCNQ is an extremely good electron acceptor, readily forming TCNQ− and TCNQ2−, electrochemical reduction of TCNQ in the presence of a transition metal ion provides an ideal method for synthesis of metal-TCNQ materials by electrocrystallization from organic solvents and ionic liquids or solid–solid transformation using TCNQ modified electrodes from aqueous media containing transition metal electrolytes. The significance of the reversible formal potential (E0f) in these studies is discussed. The coupling of electrocrystallization on electrode surfaces and microscopic characterization of the electrodeposited materials reveals a wide range of morphologies and phases which strongly influence their properties and applications. Since TCNQ can also be photo-reduced in the presence of suitable electron donors, analogous photochemical approaches to the synthesis of TCNQ-transition metal derivatives are available. The advantages of electrochemical and photochemical methods of synthesis relative to chemical synthesis are outlined.
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