The exploration of new porous hybrid materials is of great importance because of their unique properties and promising applications in separation of materials, catalysis, etc. Herein, for the first ...time, by integration of metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), a new type of MOF@COF core–shell hybrid material, i.e., NH2‐MIL‐68@TPA‐COF, with high crystallinity and hierarchical pore structure, is synthesized. As a proof‐of‐concept application, the obtained NH2‐MIL‐68@TPA‐COF hybrid material is used as an effective visible‐light‐driven photocatalyst for the degradation of rhodamine B. The synthetic strategy in this study opens up a new avenue for the construction of other MOF–COF hybrid materials, which could have various promising applications.
By integration of metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), a new type of MOF@COF core–shell hybrid material, i.e., NH2‐MIL‐68@TPA‐COF, with high crystallinity and hierarchical pore structure, is synthesized. The obtained hybrid material can be used as an effective visible‐light‐driven photocatalyst for the degradation of rhodamine B.
Rechargeable Zn-air batteries are under intensive studies because of their high-energy density, low cost, and safety. However, their wide application is prevented by several remaining technical ...issues, one of which is the lack of suitable bifunctional cathodic catalysts for oxygen reduction reaction (ORR) during discharging and oxygen evolution reaction (OER) during charging. Due to low material cost and wide distribution, carbon-based materials may serve as promising electrocatalysts, while doping heteroatoms such as nitrogen or boron can effectively enhance their catalytic activity. Herein, we pyrolyze a metal-organic framework containing Zn, N, and B as the precursor to synthesize dual-doped and metal-free porous carbon materials as efficient ORR/OER bifunctional electrocatalysts. The surface area of obtained carbon materials can be greatly enhanced by pyrolysis under H2-containing atmosphere. In addition, N and B are evenly distributed within the carbon materials due to the crystalline MOF precursor. The resultant carbon materials exhibit high ORR and OER catalytic activities in both half-cell and single-cell battery measurements. Our study has demonstrated for the first time that MOFs can be used as precursors to synthesize metal-free ORR/OER bifunctional cathodic electrocatalysts with great potential in rechargeable Zn-air batteries.
The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and ...potential applications. Herein, by elaborately designing and choosing two flexible molecules with C
molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA.
The separation of racemic molecules is of substantial significance not only for basic science but also for technical applications, such as fine chemicals and drug development. Here we report two ...isostructural chiral metal-organic frameworks decorated with chiral dihydroxy or -methoxy auxiliares from enantiopure tetracarboxylate-bridging ligands of 1,1'-biphenol and a manganese carboxylate chain. The framework bearing dihydroxy groups functions as a solid-state host capable of adsorbing and separating mixtures of a range of chiral aromatic and aliphatic amines, with high enantioselectivity. The host material can be readily recycled and reused without any apparent loss of performance. The utility of the present adsorption separation is demonstrated in the large-scale resolution of racemic 1-phenylethylamine. Control experiments and molecular simulations suggest that the chiral recognition and separation are attributed to the different orientations and specific binding energies of the enantiomers in the microenvironment of the framework.
Heterogeneous catalysts typically lack the specific steric control and rational electronic tuning required for precise asymmetric catalysis. Here we demonstrate that a phosphonate metal-organic ...framework (MOF) platform that is robust enough to accommodate up to 16 different metal clusters, allowing for systematic tuning of Lewis acidity, catalytic activity and enantioselectivity. A total of 16 chiral porous MOFs, with the framework formula M
L
(solvent)
that have the same channel structures but different surface-isolated Lewis acid metal sites, are prepared from a single phosphono-carboxylate ligand of 1,1'-biphenol and 16 different metal ions. The phosphonate MOFs possessing tert-butyl-coated channels exhibited high thermal stability and good tolerances to boiling water, weak acid and base. The MOFs provide a versatile family of heterogeneous catalysts for asymmetric allylboration, propargylation, Friedel-Crafts alkylation and sulfoxidation with good to high enantioselectivity. In contrast, the homogeneous catalyst systems cannot catalyze the test reactions enantioselectively.
Designable and ultrathin covalent organic framework nanosheets (CONs) with good photoelectric activity are promising candidates for the construction of photoelectrochemical (PEC) biosensors for the ...detection of low-abundance biological substrates. However, achieving highly sensitive PEC properties by using emerging covalent organic framework nanosheets (CONs) remains a great challenge due to the polymeric nature and poor photoelectric activity of CONs. Herein, we report for the first time the preparation of novel composites and their PEC sensing properties by electrostatic self-assembly of ultrathin CONs (called TTPA-CONs) with Ti3C2Tx. The prepared TTPA-CONs/Ti3C2Tx composites can be used as photocathodes for PEC detection of prostate-specific antigen (PSA) with high sensitivity, low detection limit, and good stability. This work not only expands the application of CONs but also opens new avenues for the development of efficient PEC sensing platforms.
Three-dimensional (3D) covalent organic frameworks (COFs) possess higher surface areas, more abundant pore channels, and lower density compared to their two-dimensional counterparts which makes the ...development of 3D COFs interesting from a fundamental and practical point of view. However, the construction of highly crystalline 3D COF remains challenging. At the same time, the choice of topologies in 3D COFs is limited by the crystallization problem, the lack of availability of suitable building blocks with appropriate reactivity and symmetries, and the difficulties in crystalline structure determination. Herein, we report two highly crystalline 3D COFs with pto and mhq-z topologies designed by rationally selecting rectangular-planar and trigonal-planar building blocks with appropriate conformational strains. The pto 3D COFs show a large pore size of 46 Å with an extremely low calculated density. The mhq-z net topology is solely constructed from totally face-enclosed organic polyhedra displaying a precise uniform micropore size of 1.0 nm. The 3D COFs show a high CO
adsorption capacity at room temperature and can potentially serve as promising carbon capture adsorbents. This work expands the choice of accessible 3D COF topologies, enriching the structural versatility of COFs.
A chiral porous metal-organic framework of an axially C2-symmetric 1,1'-biphenol ligand is constructed and can be used as a solid-state host to enanioselectively adsorb mandelates with up to 93.1% ee ...and to entrap achiral tropolone ethers and induce their asymmetric photocyclization with up to 98.5% ee.
The massive emission of CO2 has caused a series of environmental problems, including global warming, which exacerbates natural disasters and human health. Cu-based catalysts have shown great activity ...in the reduction of CO2, but the mechanism of CO2 activation remains ambiguous. In this work, we performed density functional theory (DFT) calculations to investigate the hydrogenation of CO2 on Cu(211)-Rh, Cu(211)-Ni, Cu(211)-Co, and Cu(211)-Ru surfaces. The doping of Rh, Ni, Co, and Ru was found to enhance CO2 hydrogenation to produce COOH. For CO2 hydrogenation to produce HCOO, Ru plays a positive role in promoting CO dissociation, while Rh, Ni, and Co increase the barriers. These results indicate that Ru is the most effective additive for CO2 reduction in Cu-based catalysts. In addition, the doping of Rh, Ni, Co, and Ru alters the electronic properties of Cu, and the activity of Cu-based catalysts was subsequently affected according to differential charge analysis. The analysis of Bader charge shows good predictions for CO2 reduction over Cu-based catalysts. This study provides some fundamental aids for the rational design of efficient and stable CO2-reducing agents to mitigate CO2 emission.
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