It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4. Here, Cu2O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper‐based metal–organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode) in CO2RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2O and *OCH3) involved in the pathway of CH4 formation are stabilized by the single active Cu2O(111) and hydrogen bonding, thus generating CH4 instead of CO.

The rational design of highly efficient, low-cost, and durable electrocatalysts to replace platinum-based electrodes for oxygen reduction reaction (ORR) is highly desirable. Although atomically dispersed supported metal catalysts often exhibit excellent catalytic performance with maximized atom efficiency, the fabrication of single-atom catalysts remains a great challenge because of their easy aggregation. Herein, a simple ionothermal method was developed to fabricate atomically dispersed Fe−N x species on porous porphyrinic triazine-based frameworks (FeSAs/PTF) with high Fe loading up to 8.3 wt %, resulting in highly reactive and stable single-atom ORR catalysts for the first time. Owing to the high density of single-atom Fe−N 4 active sites, highly hierarchical porosity, and good conductivity, the as-prepared catalyst FeSAs/PTF-600 exhibited highly efficient activity, methanol tolerance, and superstability for oxygen reduction reaction (ORR) under both alkaline and acidic conditions. This work will bring new inspiration to the design of highly efficient noble-metal-free catalysts at the atomic scale for energy conversion.

The electrocatalytic conversion of CO 2 into valueadded chemicals is apromising approach to realize ac arbonenergy balance.H owever,l ow current density still limits the application of the CO 2 electroreduction reaction (CO 2 RR). Metal-organic frameworks (MOFs) are one class of promising alternatives for the CO 2 RR due to their periodically arranged isolated metal active sites.H owever,t he poor conductivity of traditional MOFs usually results in al ow current density in CO 2 RR. We have prepared conductive two-dimensional (2D) phthalocyanine-based MOF (NiPc-NiO 4 )n anosheets linked by nickel-catecholate,w hichc an be employed as highly efficient electrocatalysts for the CO 2 RR to CO.T he obtained NiPc-NiO 4 has ag ood conductivity and exhibited av ery high selectivity of 98.4 %t oward CO production and al arge CO partial current density of 34.5 mA cm À2 ,o utperforming the reported MOF catalysts.T his work highlights the potential of conductive crystalline frameworks in electrocatalysis.

Electroreduction of CO 2 (CO 2 RR) into value-added fuels is of significant importance but remains a big challenge because of poor selectivity, low current density, and large overpotential. Crystalline porous covalent organic frameworks (COFs) are promising alternative electrode materials for CO 2 RR owing to their tunable and accessible single active sites. However, the poor electron-transfer capability of COFs limits their application. Herein, a tetrathiafulvalene (TTF) strut was integrated into a two-dimensional cobalt porphyrin-based COF (TTF-Por(Co)-COF) to enhance its electron-transfer capability from the TTF to the porphyrin ring. Compared with COF-366-Co without TTF, TTF-Por(Co)-COF showed enhanced CO 2 RR performance in water with 95% Faradaic efficiency of the CO 2 -to-CO conversion at −0.7 V vs RHE and a partial current density of 6.88 mA cm −2 at −0.9 V vs RHE. This work provides a new insight for the rational design of porous organic framework materials for improving the activity of CO 2 RR.

Cobalt single atoms anchored on porphyrinic triazine frameworks exhibit high activity in ORR and HER.

The electroreduction of CO2 to value‐added chemicals such as CO is a promising approach to realize carbon‐neutral energy cycle, but still remains big challenge including low current density. Covalent organic frameworks (COFs) with abundant accessible active single‐sites can offer a bridge between homogeneous and heterogeneous electrocatalysis, but the low electrical conductivity limits their application for CO2 electroreduction reaction (CO2RR). Here, a 2D conductive Ni‐phthalocyanine‐based COF, named NiPc‐COF, is synthesized by condensation of 2,3,9,10,16,17,23,24‐octa‐aminophthalocyaninato Ni(II) and tert‐butylpyrene‐tetraone for highly efficient CO2RR. Due to its highly intrinsic conductivity and accessible active sites, the robust conductive 2D NiPc‐COF nanosheets exhibit very high CO selectivity (>93%) in a wide range of the applied potentials of −0.6 to −1.1 V versus the reversible hydrogen electrode (RHE) and large partial current density of 35 mA cm−2 at −1.1 V versus RHE in aqueous solution that surpasses all the conventional COF electrocatalysts. The robust NiPc‐COF that is bridged by covalent pyrazine linkage can maintain its CO2RR activity for 10 h. This work presents the implementation of the conductive COF nanosheets for CO2RR and provides a strategy to enhance energy conversion efficiency in electrocatalysis.

Developing unique single atoms as active sites is vitally important to boosting the efficiency of photocatalytic CO 2 reduction, but directly atomizing metal particles and simultaneously adjusting the configuration of individual atoms remain challenging. Herein, we demonstrate a facile strategy at a relatively low temperature (500 °C) to access the in situ metal atomization and coordination adjustment via the thermo-driven gaseous acid. Using this strategy, the pyrolytic gaseous acid (HCl) from NH 4 Cl could downsize the large metal particles into corresponding ions, which subsequently anchored onto the surface defects of a nitrogen-rich carbon (NC) matrix. Additionally, the low-temperature treatment-induced CO motifs within the interlayer of NC could bond with the discrete Fe sites in a perpendicular direction and finally create stabilized Fe−N 4 O species with high valence status (Fe 3+ ) on the shallow surface of the NC matrix. It was found that the Fe−N 4 O species can achieve a highly efficient CO 2 conversion when accepting energetic electrons from both homogeneous and heterogeneous photocatalysts. The optimized sample achieves a maximum turnover number (TON) of 1494 within 1 h in CO generation with a high selectivity of 86.7% as well as excellent stability. Experimental and theoretical results unravel that high valence Fe sites in Fe−N 4 O species can promote the adsorption of CO 2 and lower the formation barrier of key intermediate COOH* compared with the traditional Fe−N 4 moiety with lower chemical valence. Our discovery provides new points of view in the construction of more efficient single-atom cocatalysts by considering the optimization of the atomic configuration for high-performance CO 2 photoreduction.

Electroreduction of CO 2 (CO 2 RR) to value-added chemicals offers a promising approach to balance the global carbon emission, but still remains a significant challenge due to high overpotential, low faradaic efficiency, and poor selectivity of electrocatalysts systems. Thus the key point is to develop low-cost, highly efficient, and durable electrocatalysts for CO 2 RR. To benefit from their exposed active sites and to maximize atomic efficiency, single-metal atom catalysts that usually show high activities are required. Herein, we unravel the trends in the reactivity and selectivity of atomically isolated M-N 4 (M = Ni, Cu, Fe, and Co) sites within porous porphyrinic triazine framework (metal single atoms/PTF) for the electroreduction of CO 2 to CO. We found that NiSAs/PTF exhibited the highest faradaic efficiency (98%) at a mild potential of −0.8 V versus reversible hydrogen electrode and the highest turnover frequency of 13,462 h −1 for the production CO at an applied potential of −1.2 V. The relations of catalytic performance of CO 2 to CO over the different active M-N 4 sites were unraveled by the combination of density functional theory calculations and experiments. This work gives an extensive mechanistic understanding of the selectivity of CO 2 to CO from the M-N 4 sites at an atomic scale, thus it will bring new inspiration for the design of highly efficient CO 2 RR.