Exploration of heterogeneous molecular catalysts combining the atomic-level tunability of molecular structures and the practical handling advantages of heterogeneous catalysts represents an attractive approach to developing high-performance catalysts for important and challenging chemical reactions such as electrochemical carbon dioxide reduction which holds the promise for converting emissions back to fuels utilizing renewable energy. Thus, far, efficient and selective electroreduction of CO2 to deeply reduced products such as hydrocarbons remains a big challenge. Here, we report a molecular copper-porphyrin complex (copper(II)-5,10,15,20-tetrakis(2,6-dihydroxyphenyl)porphyrin) that can be used as a heterogeneous electrocatalyst with high activity and selectivity for reducing CO2 to hydrocarbons in aqueous media. At -0.976 V vs the reversible hydrogen electrode, the catalyst is able to drive partial current densities of 13.2 and 8.4 mA cm(-2) for methane and ethylene production from CO2 reduction, corresponding to turnover frequencies of 4.3 and 1.8 molecules·site(-1)·s(-1) for methane and ethylene, respectively. This represents the highest catalytic activity to date for hydrocarbon production over a molecular CO2 reduction electrocatalyst. The unprecedented catalytic performance is attributed to the built-in hydroxyl groups in the porphyrin structure and the reactivity of the copper(I) metal center.

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Herein, we report a series of carboxyl-grafted metal–organic frameworks (UiO-66-(COOH) n , n = 0,1,2,4) for Pb2+ removal and the important role of carboxyl groups in capture of Pb2+. Among these materials, UiO-66-(COOH)2 exhibits a large adsorption capacity of 420.2 mg g–1, superior to that of other metal–organic frameworks and most of reported adsorbents. Besides, 99.99% of Pb2+ can be removed from water in the concentration range of <100 ppm with the UiO-66-(COOH)2 dosage of 0.5 mg mL–1. Furthermore, UiO-66-(COOH)2 can be easily regenerated through a simple method. Mechanism analysis (Fourier transform infrared, X-ray photoelectron spectroscopy, and density functional theory calculation) indicates that the synergy effect of rich carboxyl groups and proper pore structure plays a critical role in the capture of Pb2+. This work may provide a guideline to design high-efficiency adsorbents for Pb2+ from water.

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