Activating coordinative conjugated polymer via interfacial electron transfer for efficient CO_(2) electroreduction

With tunable local electronic environment,high mass density of MN4sites,and ease of preparation,metal-organic conjugated coordinative polymer(CCP) with inherent electronic conductivity provides a promising alternative to the well-known M-N-C electrocatalysts.Herein,the coordination reaction between Cu^(2+)and 1,2,4,5-tetraaminobenzene(TAB) was conducted on the surface of metallic Cu nanowires,forming a thin layer of CuN4-based CCP(Cu-TAB) on the Cu nanowire.More importantly,interfacial transfer of electrons from Cu core to the CuN4-based CCP nanoshell was observed within the resulting CuTAB@Cu,which was found to enrich the local electronic density of the CuN4sites.As such,the CuTAB@Cu demonstrates much improved affinity to the*COOH intermediate formed from the rate determining step;the energy barrier for C-C coupling,which is critical to convert CO_(2)into C2products,is also decreased.Accordingly,it delivers a current density of-9.1 mA cm^(-2)at a potential as high as 0.558 V(vs.RHE) in H-type cell and a Faraday efficiency of 46.4% for ethanol.This work emphasizes the profound role of interfacial interaction in tuning the local electronic structure and activating the CuN4-based CCPs for efficient electroreduction of CO_(2).

Sequence-sorted redox-switchable hetero[3]rotaxanes

From a library of five crown ether macrocycles with different ring sizes and redox-active moieties,such as tetrathiafulvalene(TTF)and naphthalene dimiide(NDI),directional heterocircuit[3]rotaxanes were constructed.Using an axle with two binding sites with different steric accessibility,the concept of integrative self-sorting was applied to program the sequence of functional units in heteropseudo[3]rotaxanes.Depending on binding strength and ring size of the smaller macrocycles,different heteropseudo[3]rotaxane selectivities and stabilities were determined by 2D NMR spectroscopy and tandem mass spectrometry.A heteropseudo[3]rotaxane with rotaxane-like behaviour was isolated chromatographically,displaying electrochemically“frustrated”properties.A robust synthetic procedure was developed allowing the synthesis of four new hetero[3]rotaxanes incorporating specific sequences of functional units.Sequence pseudoisomeric rotaxanes which have the naphthalene diimide subunit at two different positions show distinct electrochemical properties.DFT calculations suggest that this differences could arise from a folding of the structure,in which the redox-active moieties stack with a stopper unit.This study presents a blueprint for the construction of hetero[3]rotaxanes with sequential control of the functional units along the track of the axle and paves the way to extend the functionality of mechanically interlocked molecules.