China has the world's largest polyvinyl chloride (PVC) production capacity, comprising over 20 Mt a−1and occupying 41% of the world production capacity.

A highly diastereo- and enantioselective BOX/Cu(II)-catalyzed C2,C3-cyclopentannulation of indoles with donor-acceptor cyclopropanes has been developed on the basis of asymmetric formal [3 + 2] cycloaddition of indoles. This reaction provides rapid and facile access to a series of enantioenriched cyclopenta-fused indoline products and can be further extended to the construction of tetracyclic pyrroloindolines. The synthetic potential of the reaction was demonstrated in a four-step synthesis of the core structure of borreverine.

An unintended consequence of industrial nitrogen fixation through the Haber–Bosch process is nitrate (NO3 –) and nitrite (NO2 –) contamination of ocean, ground, and surface waters from fertilizer runoff. Transition-metal catalysts, particularly those based on Pd, are effective in removing NO3 –/NO2 – through reduction to N2 or NH4 +. Pd is regarded as the most effective metal for NO3 –/NO2 – reduction, and as such, few studies have thoroughly explored the performance of other transition metals as a function of varying reaction conditions. In this work, we investigated the NO2 – reduction properties of alumina-supported Rh using Pd as a benchmark, where we varied the bulk solution pH to probe the effect of reaction conditions on the catalytic chemistry. Pd expectedly showed a high reduction activity (289 L/g-surface-metal/min) and a high N2 selectivity (>99% at 20% conversion) at low pH and near inactivity at high pH. Surprisingly, the Rh catalyst, while inactive at low pH, showed moderate activity (22 L/g-surface-metal/min) and high NH4 + selectivity (>90% at 20% conversion) at high pH. Hydrazine (N2H4) was also detected as a reaction intermediate when NH4 + was formed. Microkinetic models built with energetics from density functional theory reveal that Rh catalysts are poisoned by NO* at low pH because of the rapid dissociative adsorption of protonated nitrite (HNO2) under acidic conditions, which was confirmed by in aqua surface-enhanced Raman spectroscopy. NO* poisoning of the Rh surface lessens at increased solution pH because NO2 – does not dissociate as readily compared to HNO2, which explains why Rh exhibits higher activity in basic solutions. The microkinetic models further elucidate the competition between N2H4 and NH3/NH4 + formation as a function of pH, where we find that hydrogen surface coverage dictates product selectivity. These results update the common view that only Pd-based catalysts are effective for NO2 – reduction and suggest unexplored avenues for nitrogen chemistry.

Poly­(acrylic acid) (PAA) hydrogels with a multi-bond network composed of sparse chemical cross-links and carboxyl-Fe3+ coordination are prepared through a controllable permeation strategy utilizing ferric citrate (FeCA). The existing strategies that directly soak PAA hydrogels in Fe3+ solutions usually induce an inhomogeneous network with densely cross-linked shells and uncertain water content of the hydrogels, which brings about ambiguity when investigating strengthening mechanisms because water content significantly affects the mechanical properties of hydrogels. Herein, the controllable permeation of Fe3+ into PAA networks based on the competition between citric acid (CA)-Fe3+ chelation and PAA-Fe3+ coordination guarantees sustained release of Fe3+, facilitating homogeneous distribution of ionic cross-links and a certain water content. The obtained hydrogels exhibit excellent and balanced mechanical properties (high tensile strength of 3.28 to 6.95 MPa with large elongations at break of 1400 to 780% when water content decreases from 80 to 50 wt %). The real robust tensile strength of this hydrogel originates from the effective energy dissipation of the homogeneous PAA-Fe3+ cross-links, and the high water content ensures a large elongation at break. Furthermore, the hydrogel also has pH-responsive and shape-memory properties.