Three-dimensional
covalent organic frameworks (3D-COFs) are emerging
as designable porous materials because of their unique structural
characteristics and porous features. However, because of the lack
of 3D organic building units and the less reversible covalent bonds,
the topologies of 3D-COFs to date have been limited to dia, ctn, ffc, bor, rra, srs, pts, lon, stp, acs, tbo, bcu, and fjh. Here we report a 3D-COF with the ceq topology
utilizing a D
3h
-symmetric
triangular prism vertex with a planar triangular linker. The as-synthesized
COF displays a twofold-interpenetrated structure with a Brunauer–Emmett–Teller
surface area of 1148.6 m2 g–1. Gas sorption
measurements revealed that 3D-ceq-COF could efficiently absorb CO2, CH4, and H2 under a moderate surface
area. This work provides new building units and approaches for structural
and application exploration of 3D-COFs.
Lithium reactivity with electrolytes leads to their continuous consumption and dendrite growth, which constitute major obstacles to harnessing the tremendous energy of lithium-metal anode in a reversible manner. Considerable attention has been focused on inhibiting dendrite via interface and electrolyte engineering, while admitting electrolyte-lithium metal reactivity as a thermodynamic inevitability. Here, we report the effective suppression of such reactivity through a nano-porous separator. Calculation assisted by diversified characterizations reveals that the separator partially desolvates Li+ in confinement created by its uniform nanopores, and deactivates solvents for electrochemical reduction before Li0-deposition occurs. The consequence of such deactivation is realizing dendrite-free lithium-metal electrode, which even retaining its metallic lustre after long-term cycling in both Li-symmetric cell and high-voltage Li-metal battery with LiNi0.6Mn0.2Co0.2O2 as cathode. The discovery that a nano-structured separator alters both bulk and interfacial behaviors of electrolytes points us toward a new direction to harness lithium-metal as the most promising anode.
Rhenium(I)-carbonyl-diimine complexes have emerged as promising photocatalysts for carbon dioxide reduction with covalent organic frameworks recognized as perfect sensitizers and scaffold support. Such Re complexes/covalent organic frameworks hybrid catalysts have demonstrated high carbon dioxide reduction activities but with strong excitation energy-dependence. In this paper, we rationalize this behavior by the excitation energy-dependent pathways of internal photo-induced charge transfer studied via transient optical spectroscopies and time-dependent density-functional theory calculation. Under band-edge excitation, the excited electrons are quickly injected from covalent organic frameworks moiety into catalytic RheniumI center within picosecond but followed by fast backward geminate recombination. While under excitation with high-energy photon, the injected electrons are located at high-energy levels in RheniumI centers with longer lifetime. Besides those injected electrons to RheniumI center, there still remain some long-lived electrons in covalent organic frameworks moiety which is transferred back from RheniumI. This facilitates the two-electron reaction of carbon dioxide conversion to carbon monoxide.
Three-dimensional (3D) covalent organic frameworks (COFs) are a new type of crystalline organic porous material, which have great application potential in various fields due to their complex pore structures and fully exposed active sites. The synthesis of 3D COFs with novel topologies is still challenging on account of limited secondary building units. Herein, we report a 3D COF with hea topology, which has never been reported before, utilizing a D 3hsymmetric precursor [2,3,6,7,14,15-hexakis(4-formylphenyl)triptycene (HFPTP)] and [tetrakis(4-amino biphenyl)methane (TABPM)]. 3Dhea-COFs display permanent porosity and a Brunauer−Emmett− Teller surface area of 1804.0 m 2 g −1 . Owing to the huge internal free volume of triptycene, 3D-hea-COFs show good adsorption performance for H 2 , CO 2 , and CH 4 . Moreover, theoretical calculation reveals that both triptycene and tetraphenylmethane units contribute to enhance hydrogen storage capacity. The novel topology in this work expands the family of 3D COFs and provides new possibilities for designing efficient gas storage materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.