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The shuttle effect of polysulfides poses a significant obstacle to the commercialization of lithium-sulfur (Li–S) batteries. Covalent organic frameworks have been widely used in Li–S batteries as porous crystalline materials to suppress the shuttle effect. Herein, a 3,5-bis(trifluoromethyl)benzyl (BTFMB-TzDa) modified triazine-based covalent organic framework was synthesized. The high electronegativity and large steric hindrance of the BTFMB-TzDa modified separator successfully suppressed the diffusion of polysulfides, leading to improved capacity and cyclic stability of Li–S batteries. Cells with the BTFMB-TzDa modified separator exhibited a high initial capacity of 1205 mA h g−1 at 0.2C and 657 mA h g−1 at 3.0C. Furthermore, the capacity still remained at 501 mA h g−1 after 500 cycles. The BTFMB-TzDa modified separator provides an alternative strategy for the construction of high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]

A stable nanoscaled single-excitation ratiometric luminescent pH sensor (MPDB-PCN) over a broad pH range from 2.5 to 8.6 is fabricated through post-synthetic modification of PCN-224 with naphthalimide-derived molecules. Due to the rapid, sensitive and linear response to pH, MPDB-PCN is capable of detecting 3-nitropropionic acid (3-NPA), an acid neurotoxin in food safety, with a low detection limit of 15 μM in sugarcane juice. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have shown great potential for use in ion sensing; however, applications of existing COFs are limited to sensing either cations or anions. In this study, a three-dimensional COF, COF-TT, is constructed by reacting the bis(tetraoxacalix[2]arene[2]triazine) core with tetra(p-aminophenyl)methane to provide a luminescent sensor. COF-TT exhibits ultrahigh thermal stability and exceptional chemical stability in aqueous solutions over a broad pH range from 2 to 14, which signifies immense practical potential for sensing applications. Excellent selectivity and high sensitivity of COF-TT toward Fe3+ cations and CrO42−, Cr2O72−, and MnO4− anions are evident via luminescence quenching. COF-TT also exhibits excellent recyclability in terms of washing and re-exposure cycles. Both experimental data and theoretical calculations are employed to unveil the mechanisms of the quenching effect and sensing properties of COF-TT. [ABSTRACT FROM AUTHOR]