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The covalent organic frameworks/polymers configurated with metal‐N4 conjugated structures offer an exceptional platform for efficient electrochemical CO2 reduction reaction (eCO2RR). However, understanding the impact of the structure‐mediated local microenvironment and integrating CO2 electroreduction with follow‐up utilization toward extending chemical valorization of CO2 are still far from sufficient. Herein, a set of covalent phenanthroline‐porphyrin polymers are designed to decode the microenvironment modulation originating from built‐in structures, and the optimized one delivered an extraordinary performance for eCO2RR with ≈100% Faradaic efficiency of CO under stabilized CO2‐electrolysis of 70 h. The experimental and theoretical analyses suggest that the regulation of the Co‐N4 electronic structures and microenvironment convoys the stabilized formation of key reaction intermediate *COOH. Furthermore, through CO‐mediated electro/thermocatalytic tandem processes, the aminocarbonylation of aryl iodides and amines with high yields has been convincingly implemented over the coordinated Pd sites, which is remarkably helpful to propel extending chemical valorization of CO2. [ABSTRACT FROM AUTHOR]

The electrochemical carbon dioxide reduction reaction (CO2RR) converting CO2 into value‐added chemicals and fuels to realize carbon recycling is a solution to the problem of renewable energy shortage and environmental pollution. Among all the catalysts, the carbon‐based single‐atom catalysts (SACs) with isolated metal atoms immobilized on conductive carbon substrates have shown significant potential toward CO2RR, which intrigues researchers to explore high‐performance SACs for fuel and chemical production by CO2RR. Especially, regulating the coordination structures of the metal centers and the microenvironments of the substrates in carbon‐based SACs has emerged as an effective strategy for the tailoring of their CO2RR catalytic performance. In this review, the current in situ/operando study techniques and the fundamental parameters for CO2RR performance are first briefly presented. Furthermore, the recent advances in synthetic strategies which regulate the atomic structures of the carbon‐based SACs, including heteroatom coordination, coordination numbers, diatomic metal centers, and the microenvironments of substrates are summarized. In particular, the structure‐performance relationship of the SACs toward CO2RR is highlighted. Finally, the inevitable challenges for SACs are outlined and further research directions toward CO2RR are presented from the perspectives. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 to valuable fuels is appealing for CO2 fixation and energy storage. However, the development of electrocatalysts with high activity and selectivity in a wide potential window is challenging. Herein, atomically thin bismuthene (Bi‐ene) is pioneeringly obtained by an in situ electrochemical transformation from ultrathin bismuth‐based metal–organic layers. The few‐layer Bi‐ene, which possesses a great mass of exposed active sites with high intrinsic activity, has a high selectivity (ca. 100 %), large partial current density, and quite good stability in a potential window exceeding 0.35 V toward formate production. It even deliver current densities that exceed 300.0 mA cm−2 without compromising selectivity in a flow‐cell reactor. Using in situ ATR‐IR spectra and DFT analysis, a reaction mechanism involving HCO3− for formate generation was unveiled, which brings new fundamental understanding of CO2 reduction. [ABSTRACT FROM AUTHOR]

• A single-atom catalyst with ultrathin nanosheet structure and high Ni loading of 5.92 wt%. • High catalytic performance with CO Faradaic efficiency over 95 % in a wide potential range. • Remarkable CO yields up to 1146 mmol g cat –1 h–1. • Unveiling modulation effect of the electronic configuration of Ni-N 4 active sites by F-doping. A fluorine-tuned single-atom catalyst with an ultrathin nanosheet morphology (only ∼1.25 nm) and high Ni content of 5.92 wt% was fabricated by a polymer-assisted pyrolysis approach. The synthetic approach not only controls the establishment of the ultrathin nanosheet structure for achieving high surface communication, but also incorporates F dopants to manipulate the electronic structure of the metalloporphyrin-like active sites (Ni-N 4). As a result, such catalyst with unique structural features exhibits a remarkable electrocatalytic performance for CO 2 -to-CO conversion with the Faradaic efficiency (FE) over 95 % in a wide potential range and an outstanding CO evolution rate of 1146 mmol g cat –1 h–1 at –0.97 V vs. RHE. The in situ attenuated total reflection-infrared spectroscopy (ATR-IR) and theoretical calculations further demonstrate that the F-doping modulates the electron configuration of the central Ni-N 4 sites and thereby reduces the energy barrier for CO 2 activation, which is favorable to the generation of the key *COOH intermediate. [ABSTRACT FROM AUTHOR]

• Immobilization of the functionalized phthalocyanine at the single-molecular level. • Nearly 100 % Faradaic efficiency for electrocatalytic CO 2 reduction. • A ultrahigh CO/H 2 ratio of 640 at –0.88 V. How to efficiently obtain the value-added products through electrocatalytic CO 2 reduction is highly desired while remains significant challenges. Herein, we report an extremely active and selective immobilized pyrrolidinonyl nickel phthalocyanine (PyNiPc) catalyst for electrocatalytic CO 2 reduction, which was constructed by a built-in pyrrolidone group-assisted assembly strategy and presented single-molecular level dispersion of PyNiPc on carbon nanotubes. The resulting catalyst can predominantly produce CO in the electrocatalytic CO 2 reduction, affording nearly 100 % Faradaic efficiency over a wide potential range with ultrahigh CO/H 2 ratios up to 640. Besides, the extraordinary activity with a turnover frequency value of 1.3 × 104 h–1 at –0.93 V and durability were also achieved. Investigations unraveled the promotion effect of pyrrolidone groups in dispersion and catalysis. The reaction pathways over this catalyst were further explored by using in situ attenuated total reflection-infrared spectroscopy. This work offers a new understanding for constructing both active and selective molecular-based electrocatalysts. [ABSTRACT FROM AUTHOR]

The covalent organic frameworks/polymers configurated with metal‐N4 conjugated structures offer an exceptional platform for efficient electrochemical CO2 reduction reaction (eCO2RR). However, understanding the impact of the structure‐mediated local microenvironment and integrating CO2 electroreduction with follow‐up utilization toward extending chemical valorization of CO2 are still far from sufficient. Herein, a set of covalent phenanthroline‐porphyrin polymers are designed to decode the microenvironment modulation originating from built‐in structures, and the optimized one delivered an extraordinary performance for eCO2RR with ≈100% Faradaic efficiency of CO under stabilized CO2‐electrolysis of 70 h. The experimental and theoretical analyses suggest that the regulation of the Co‐N4 electronic structures and microenvironment convoys the stabilized formation of key reaction intermediate *COOH. Furthermore, through CO‐mediated electro/thermocatalytic tandem processes, the aminocarbonylation of aryl iodides and amines with high yields has been convincingly implemented over the coordinated Pd sites, which is remarkably helpful to propel extending chemical valorization of CO2. [ABSTRACT FROM AUTHOR]

Herein, a hierarchically ordered porous superstructure of N-doped carbon embedded with readily accessible Fe-Ni diatomic sites (FeNi DASs/HOPSNC) has been synthesized for highly efficient CO 2 electroreduction. By integrating additional secondary mesopores into the ordered macroporous skeleton, this distinctive superstructure exhibits greatly enhanced accessibility and mass transfer. Benefiting from the unique structure merits including the synergistic effect in Fe-Ni atomic pair sites and the multi-level porosity, such diatomic site catalyst affords an outstanding electrocatalytic performance with excellent activity and selectivity for CO 2 -to-CO conversion and remarkable stability. Furthermore, systematic characterizations and density functional theory calculations unveiled that the electronic interaction within the diatomic pairs leads to the optimized electronic state and decreased reaction energy barrier for generating COOH* intermediate and weakening the binding strength of CO*, thereby improving the intrinsic catalytic activity and selectivity. This work may inspire further development of high-performance diatomic site catalysts for CO 2 electroreduction and other electrosynthesis. [Display omitted] • A hierarchically ordered porous superstructure with readily accessible atomic pair sites is constructed. • The ordering and uniformity of multiscale pores in MOF-derived carbon materials is controlled. • The Fe-Ni diatomic catalyst (DAC) shows synergistic electronic interaction between the two adjacent metal atoms. • A high Faradaic efficiency of 94.5%, large current densities up to 300 mA cm−2 and remarkable durability are obtained. [ABSTRACT FROM AUTHOR]