A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in mediating a 2-picolylazide-involved AAC reaction than the fully reduced Cu(OAc)2. Finally, the discontinuous kinetic behavior that has been observed by us and others in copper(I/II)-mediated AAC reactions is explained by the likely catalyst disintegration during the course of a relatively slow reaction. Complementing the prior mechanistic conclusions drawn by other investigators which primarily focus on the copper(I)/alkyne interactions, we emphasize the kinetic significance of copper(I/II)/azide interaction. This work not only provides a mechanism accounting for the fast Cu(OAc)2-mediated AAC reactions involving chelating azides, which has apparent practical implications, but suggests the significance of mixed-valency dinuclear copper species in catalytic reactions where two copper centers carry different functions.

We described in a previous communication (ref. 13) a variant of the popular Cu I -catalyzed azidealkyne cycloaddition (AAC) process where 5 mol% Cu(OAc) 2 in the absence of any added reducing agent is sufficient to enable the reaction. 2-Picolylazide (1) and 2-azidomethylquinoline (2) were found to be by far the most reactive carbon azide substrates that convert to 1,2,3-triazoles in as short as a few minutes under the discovered conditions. We hypothesized that the abilities of 1 and 2 to chelate Cu II contribute significantly to the observed high reaction rates. The current work examines the effect of auxiliary ligands near the azido group other than pyridyl for Cu II on the efficiency of the Cu(OAc) 2 -accelerated AAC reaction. The carbon azides capable of binding to the catalytic copper center at the alkylated azido nitrogen in a chelatable fashion were indeed shown to be superior substrates under the reported conditions. The chelation between carbon azide 11 and Cu II was demonstrated in an X-ray single crystal structure. In a limited set of examples, the ligand tris (benzyltriazolylmethyl)amine (TBTA), developed by Fokin et al. for assisting the original Cu Icatalyzed AAC reactions (ref. 8), also dramatically enhances the Cu(OAc) 2 -accelerated AAC reactions involving non-chelating azides. This observation leads to the hypothesis of an additional effect of chelating azides on the efficiencies of Cu(OAc) 2 -accelerated AAC reactions, which is to facilitate the rapid reduction of Cu II to highly catalytic Cu I species. Mechanistic studies on the AAC reactions with particular emphasis on the role of carbon azide/copper interactions will be conducted based on the observations reported in this work. Finally, the immediate utility of the product 1,2,3-triazole molecules derived from chelating azides as multidentate metal coordination ligands is demonstrated. The resulting triazolyl-containing ligands are expected to bind with transition metal ions via the N(2) nitrogen of the 1,2,3-triazolyl group to form non-planar coordination rings. The Cu II complexes of bidentate T1 and tetradenetate T6, and the Zn II complex of T6 were characterized by X-ray crystallography. The structure of [Cu(T1) 2 (H 2 O) 2 ](ClO 4 ) 2 reveals the interesting synergistic effect of hydrogen bonding, π-π stacking interactions, and metal coordination in forming a one-dimensional supramolecular construct in the solid state. The tetradentate coordination mode of T6 may be incorporated into designs of new molecule sensors and organometallic catalysts.

Two novel BODIPY-based conjugated porous polymers were prepared for the adsorption of volatile iodine.

We report the preparation of a highly fluoro-substituted crystalline covalent organic framework (COF) and its application as a cathode material in lithium–sulfur batteries (LSBs) upon sulfur confinement. A sulfur-functionalized COF with high sulfur content (60 wt %) was obtained through physisorption of elemental sulfur and subsequent SNAr reaction of sulfur with aromatic fluorides on the COF backbone. After such physical and chemical confinement of sulfur through a postfunctionalization approach, the COF material still shows some structural order, allowing us to investigate the structure–property relationship of such COF materials in LSB application. We compared the electrochemical performances of the two cathode materials prepared from a crystalline COF and its amorphous counterpart and studied the important factors that affect battery capacity, reaction kinetics, and cycling stability.

Metal-free and heterogeneous organic photocatalysts provide an environmentally friendly alternative to traditional metal-based catalysts. This paper reports a series of carbazole-based conjugated microporous polymers (CMPs) with tunable redox potentials and explores their photocatalytic performance with regard to C-3 formylation and thiocyanation of indoles. Conjugated polymers were synthesized through FeCl3 mediated Friedel–Crafts reactions, and their redox potentials were well regulated by simply altering the nature of the core (i.e., 1,4-dibenzyl, 1,3,5-tribenzyl, or 1,3,5-triazin-2,4,6-triyl). The resulting CMPs exhibited high surface areas, visible light absorptions, and tunable semiconductor-range band gaps. With the highest oxidative capability, CMP-CSU6 derived from 1,3,5-tri­(9H-carbazol-9-yl)­benzene showed the highest efficiency for C-3 formylation and thiocyanation of indoles at room temperature. Notably, the as-made catalysts can be easily recovered with good retention of photocatalytic activity and reused at least five times, suggesting good recyclability. These results are significant for constructing high-performance porous polymer catalysts with tunable photoredox potentials targeting an efficient material design for catalysis.

Building an artificial interphase layer for tackling uncontrollable Zn dendrites and serious side reactions is a highly desirable strategy, but it is often hampered by the limited Zn 2+ transport. Here, a stable fluorine-doped amorphous carbon (CF) artificial layer is constructed on a Cu current collector (CF-Cu) via facile carbonization treatment of a fluoropolymer coating to realize underlying Zn deposition. As evidenced experimentally and theoretically, this inorganic CF layer with ionic conductivity and electronic insulation successfully triggers dendrite-free Zn deposition at the CF-Cu interface with preferred Zn(002) crystal plane stacking parallel to the substrate surface, thus greatly promoting the inhibition of Zn-dendrites and blocking of interfacial side reactions. The introduced fluorine atoms as abundant zincophilic sites play an important role in driving fast zinc-ion transfer kinetics, which can partly convert into ZnF 2 as an artificial solid Zn 2+ conductor to further guide uniform Zn deposition. Consequently, the CF-Cu electrode enables high reversibility with 99% coulombic efficiency and a long cycling stability of 1900 cycles at 2 mA cm -2 . The integrated CF-Cu@Zn anode achieves up to 2200 h cycles with a low voltage polarization. This study provides inspiration for the design of artificial interphase layers for stable nondendritic metal batteries.

A series of thermo-and pH-dual responsive dendronized polymers PSADG1-PSADG3 were successfully synthesized by attaching butylamide terminated poly(amidoamine) dendrons (DG1-DG3) to the alternating copolymers of styrene (St) and maleic anhydride (MAh). The structures and the molecular weights of the obtained polymers were characterized by 1 H NMR and FTIR. The coverage degrees of DG1-DG3 dendrons were 83.5%, 64.9%, and 60.5%, respectively, indicating that the numbers of the attaching dendrons decreased in the order of G1 > G2 > G3. The turbidity measurements revealed that all the dendronized polymers exhibited reversible thermo-responsive property in deionized water, and the LCST values increased from PSADG1 to PSADG3 due to both the coverage degree and the structure of dendrons. Moreover, these dendronized polymers were sensitive to pH on account of the carboxylic and tertiary amino groups in the architecture. It has been found that, for example, the PSADG2 did not display thermal sensitivity in acidic environment (pH 2.4), whereas the phase transition occurred in near neutral (pH 6.0) and basic conditions (pH 10.6) with the LCST of 33.1 and 49.0°C, respectively. It was also found that, at pH 6.0, the polymers formed larger aggregates with R h,app of ca. 0.6 μm at elevated temperatures mainly because of the dehydration and the enhanced hydrophobic interactions. The morphology of the aggregates was monitored by optical microscopy, and uniform spherical aggregates with a diameter of 5-10 μm were observed above the LCST.

The synthetic control over pore structure remains highly desirable for porous organic frameworks. Here, we present a competitive chemistry strategy, i.e., a systematical regulation on Friedel–Crafts reaction and Scholl coupling reaction through tuning the ratios of monomers. This leads to a series of spirobifluorene-based microporous polymers (Sbf-TMPs) with systematically tuned porosities and N content. Unlike the existing copolymerization strategy by which the synthesized polymers exhibit a monotonic change tendency in the porosities, our networks demonstrate an unusually different trend where the porosity increases first and then decreases with the increasing Ph/Cl ratios for the monomers. This is mainly ascribed to the completion of coexisting reaction routines and the different “internal molecular free volumes” of the repeating units. The as-made networks feature tunable capacities for CO2 adsorption over a wide range and attractive CO2/N2 selectivities. Moreover, these donor–acceptor type frameworks exhibit selective and highly sensitive fluorescence-on or fluorescence-off properties toward volatile organic compounds, which implies their great potential in fluorescent sensors.