The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been ...developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.
A host–guest cooperative protection strategy has been developed for constructing single‐atom catalysts (SACs), extending the range of available precursors from nitrogenous to non‐nitrogenous MOFs. The obtained Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) at different pyrolysis temperatures feature varying nitrogen coordination numbers. The best of these catalysts, NiSA‐N2‐C, shows superior activity and selectivity in CO2 electroreduction.
While catalysis is highly dependent on the electronic structure of the catalyst, the understanding of catalytic performance affected by electron spin regulation remains challenging and rare. Herein, ...we have developed a facile strategy to the manipulation of the cobalt spin state over covalent organic frameworks (COFs), COF-367-Co, by simply changing the oxidation state of Co centered in the porphyrin. Density functional theory (DFT) calculations together with experimental results confirm that CoII and CoIII are embedded in COF-367 with S = 1/2 and 0 spin ground states, respectively. Remarkably, photocatalytic CO2 reduction results indicate that COF-367-CoIII exhibits favorable activity and significantly enhanced selectivity to HCOOH, accordingly much reduced activity and selectivity to CO and CH4, in sharp contrast to COF-367-CoII. The results highlight that the spin-state transition of cobalt greatly regulates photocatalytic performance. Theoretical calculations further disclose that the presence of CoIII in COF-367-Co is preferable to the formation of HCOOH but detrimental to its further conversion, which clearly accounts for its distinctly different photocatalysis over COF-367-CoII. To the best of our knowledge, this is the first report on regulating photocatalysis by spin state manipulation in COFs.
Covalent organic frameworks (COFs), constructed by organic building blocks through strong covalent bonds, featuring well-defined structures, excellent stability and desired semiconductor-like ...behavior, have been employed for extensive potential applications, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs such as diversity, tailorability, stability and porosity. Whereafter, the advantages and fundamentals of COFs in photocatalysis are introduced. Furthermore, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Particularly, diverse strategies for improving photocatalytic performance and the corresponding structure-activity relationships are highlighted. Finally, the challenges and future prospects for the development of efficient COF-based photocatalysts are briefly indicated.
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•An overview of the introduction of different methods for the synthesis of COFs.•The structural features of COFs including diversity, tailorability, stability and porosity.•The advantages and fundamentals of COFs in photocatalysis.•Photocatalytic applications of COF-based materials in the fields of H2 production, CO2 reduction, organic transformation and pollution degradation.•The challenges and opportunities for the development of COF-based photocatalysts.
Covalent organic frameworks (COFs) are a new class of crystalline porous materials obtained from covalently attached organic building units. By virtue of the unique characteristics such as periodic and well-defined structures, low-density, high surface area, excellent stability as well as desired semiconductor-like behavior, COFs have gained tremendous attention for functional applications in many fields, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs including diversity, tailorability, stability and porosity are provided. Afterwards, the fundamentals and advantages of COFs for photocatalysis are briefly introduced. Following this, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Meanwhile, a series of strategies are highlighted to improve photocatalytic performance for the understanding of the structure-property relationship in this part. Finally, the remaining challenges and prospects on further development of efficient COF-based photocatalysts are indicated.
Dual‐atom catalysts (DACs) have emerged as efficient electrocatalysts for CO2 reduction owing to the synergistic effect between the binary metal sites. However, rationally modulating the electronic ...structure of DACs to optimize the catalytic performance remains a great challenge. Herein, we report the electronic structure modulation of three Ni2 DACs (namely, Ni2−N7, Ni2−N5C2 and Ni2−N3C4) by the regulation of the coordination environments around the dual‐atom Ni2 centres. As a result, Ni2−N3C4 exhibits significantly improved electrocatalytic activity for CO2 reduction, not only better than the corresponding single‐atom Ni catalyst (Ni−N2C2), but also higher than Ni2−N7 and Ni2−N5C2 DACs. Density functional theory (DFT) calculations revealed that the high electrocatalytic activity of Ni2−N3C4 for CO2 reduction could be attributed to the electronic structure modulation to the Ni centre and the resulted proper binding energies to COOH* and CO* intermediates.
Three Ni2 dual‐atom catalysts (DACs) with electronic structures tailored by the regulation of the coordination environment of Ni atoms, have been prepared for electrocatalytic CO2 reduction. The optimal Ni2−N3C4 exhibits the highest performance for the reduction of CO2 to CO, highlighting the significance of the electronic structure for electrocatalytic CO2 reduction in DACs.
Over the past decade, lanthanide compounds have become of increasing interest in the field of Single Molecule Magnets (SMMs) due to the large inherent anisotropy of the metal ions. Heavy lanthanide ...metal systems, in particular those containing the dysprosium(III) ion, have been extensively employed to direct the formation of a series of SMMs. Although remarkable progress is being made regarding the synthesis and characterization of lanthanide-based SMMs, the understanding and control of the relaxation dynamics of strongly anisotropic systems represents a formidable challenge, since the dynamic behaviour of lanthanide-based SMMs is significantly more complex than that of transition metal systems. This perspective paper describes illustrative examples of pure dysprosium(III)-based SMMs, published during the past three years, showing new and fascinating phenomena in terms of magnetic relaxation, aiming at shedding light on the features relevant to modulating relaxation dynamics of polynuclear lanthanide SMMs.
A stable porous metal-organic framework (MOF) containing methyl viologen cations exhibits reversible photochromic, thermochromic and fluorescence changes via host-guest interactions, and can be used ...for fast and selective detection of oxygen by naked eye recognition of color change within five seconds.
Catalysts featuring dinuclear metal sites are regarded as superior systems compared with their counterparts with mononuclear metal sites. The dinuclear metal sites in catalysts with appropriate ...spatial separations and geometric configurations can confer the dinuclear metal synergistic catalysis (DMSC) effect, and thus boost the catalytic performance, in particular for reactions involving multiple reactants, intermediates and products. In this review, we summarize the related reports on the design and synthesis of both homogeneous and heterogeneous dinuclear metal catalysts, and their applications in energy conversion reactions, including photo-/electro-catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO
2
reduction reaction (CO
2
RR), and N
2
reduction reaction (N
2
RR). Particularly, we focus on the analysis of the relationship between the catalyst structure and catalytic performances, where the design principles are presented. Finally, we discuss the challenges in the design and preparation of dinuclear metal catalysts with the DMSC effect and present a perspective on the future development of dinuclear metal catalysts in energy conversion. This review aims to comprehensively summarize the up-to-date research progress on the synthesis and energy-related application of dinuclear metal catalysts and provide guidance for designing energy-conversion catalysts with superior performances.
An exclusive review focusing on catalysts exhibiting the dinuclear metal synergistic catalysis (DMSC) effect for energy conversion reactions is presented.
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), featuring porous crystalline materials, have attracted tremendous attention for various applications due to their periodic and ...well-defined structures, high surface area, and tunable pore architectures. In particular, the facile modification of MOFs and COFs enables their intermesh into MOF/COF hybrids to enhance performance and/or extend scope toward diverse applications. In this review, we provide an overview of significant progress in the design and synthesis of MOF/COF hybrids, including MOF@COF, COF@MOF, MOF + COF, C-MOF, and COF-in-MOF, and their various applications in catalysis, gas adsorption, sensing, energy storage, and photodynamic therapy. The challenges and prospects of the construction of MOF/COF hybrids for various applications are also briefly discussed.
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The chemistry of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), collectively referred to as reticular chemistry, has become one of the fastest growing fields of chemistry and materials science. As two important pillars in reticular chemistry, MOFs and COFs have developed in parallel along their respective trajectories for around 2–3 decades, resulting in >80,000 MOFs with >2,000 topologies and >500 COFs with >18 topologies being reported. The integration of structures and functions of these MOFs and COFs will greatly enrich their structures and properties and expand their applications. In addition, the results of integration may also in turn enlighten and promote the development of single MOFs and/or COFs. This review presents an overview of significant progress in the design, synthesis, and applications of MOF/COF hybrid materials. Moreover, the future direction of the nascent field is pointed out.
The structure and function integration of MOFs and COFs will greatly enrich their structures and properties and expand their applications. This review presents an overview of significant progress in the design, synthesis, and applications of MOF/COF hybrid materials. In addition, the challenges and prospects of the nascent field are briefly discussed.
Magnetic personality: The incorporation of a bulky auxiliary ligand in β‐diketone‐based dysprosium(III) single‐ion magnets (SIMs) remarkably increases the anisotropic barriers, representing a ...promising route toward the design of higher‐anisotropic‐barrier SIMs (see scheme).
A dynamic fluorescent metal-organic framework has been constructed using triphenylene-2,6,10-tricarboxylate and Tb(3+) as building blocks, which exhibits guest-responsive structural dynamism and ...selective sensing of nitroaromatic explosives.
