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[Display omitted] • Cobalt protoporphyrin (CoPpIX) grafted MIL-101(Cr)–NH 2 was constructed through facile post-synthetic modification. • The porphyrins are covalently linked to amino groups of the parent MOF without impairing its well-defined porous framework. • The parent MOF with superior CO 2 capture ability exposes Co porphyrins to elevated local CO 2 concentration by CO 2 enrichment. • A remarkably high CO Faradaic efficiency of 97.1% and a turnover frequency up to 0.63 s−1 are achieved. Electrocatalytic carbon dioxide reduction reaction (CO 2 RR) presents a sustainable route to address energy crisis and environmental issues, where the rational design of catalysts remains crucial. Metal–organic frameworks (MOFs) with high CO 2 capture capacities have immense potential as CO 2 RR electrocatalysts but suffer from poor activity. Herein we report a redox-active cobalt protoporphyrin grafted MIL-101(Cr)–NH 2 for CO 2 electroreduction. Material characterizations reveal that porphyrin molecules are covalently attached to uncoordinated amino groups of the parent MOF without compromising its well-defined porous structure. Furthermore, in situ spectroscopic techniques suggest inherited CO 2 concentrate ability and more abundant adsorbed carbonate species on the modified MOF. As a result, a maximum CO Faradaic efficiency (FE CO) up to 97.1% and a turnover frequency of 0.63 s−1 are achieved, together with FE CO above 90% within a wide potential window of 300 mV. This work sheds new light on the coupling of MOFs with molecular catalysts to enhance catalytic performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective Cu-MOFs containing missing linkers were constructed. • Local atomic structure, bonding features and electronic configuration were elaborately tailored. • Tuned microenvironments mediate the reconstruction-generation of abundant undercoordinated Cu species. • Increased *CO coverage and stabilized C 2 intermediates on defective Cu sites. • Promoted C–C coupling fosters remarkable CO 2 -to-C 2+ performance of UC-Cu-BTEC. Electrocatalytic CO 2 reduction reaction (CO 2 RR) presents a promising strategy to alleviate energy and environmental crisis, where upgrading CO 2 into multicarbon (C 2+) chemicals is greatly favored. Cu-based catalysts have been showing attractive potential for C 2+ production and yet remain to achieve advanced performances and clarify actual mechanisms. Herein, defect-engineered Cu-based metal–organic frameworks (MOFs) with missing linkers (UC-Cu-BTEC) are constructed as electrocatalysts for CO 2 RR. The presence of linker vacancies leads to distorted Cu dimers and undercoordinated Cu ions, demonstrating a feasible strategy to regulate the local atomic structure, bonding features and electronic configurations of active sites. The Faradaic efficiency of C 2+ on UC-Cu-BTEC reaches 77.2 % and maintains above 70 % within a wide potential window of 400 mV, far beyond that of pristine MOFs. The partial current density of C 2+ under neutral conditions in a flow cell amounts to −153.5 mA cm−2. By in situ X-ray absorption spectroscopy and Raman spectroscopy, it is unveiled that abundant undercoordinated Cu species have been generated by the reconstruction of defective Cu dimers during CO 2 RR, which improves *CO coverage and stabilizes C 2 intermediates, thus promoting C–C coupling and enhancing the CO 2 -to-C 2+ performance. This work sheds new light on engineering the coordination microenvironments of active sites and designing defective MOFs for tailored functions. [ABSTRACT FROM AUTHOR]

CO 2 photoreduction performance of CeO 2 has been markedly enhanced by Y doping, which is achieved by the introduction of abundant oxygen vacancies and the intermediate regulations on the catalyst. [Display omitted] • Doping in CeO 2 results in promoted CO 2 photoreduction to CO. • Doping in CeO 2 results in differential generation/transformation of intermediates. • CO 2 adsorption/activation facilitates generation/transformation of intermediates. • The intermediates accumulation is the main obstacle to achieve sustainable activity. Doping hetero-metal ions in semiconductors, especially metal oxides, is a common practice to elevate their photocatalytic reduction activity. However, the underlying enhancement mechanism of doping different metal ions into the host lattice on photocatalytic CO 2 reduction has been rarely explored and thus remains unclear. In this work, CeO 2 nanoparticles doped with three different metal ions (Ce M , M = Y, La, Mo) have been synthesized, which exhibited significantly improved photo-reduction CO 2 activity. According to the analysis of Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), Y and Mo doping results in increased oxygen vacancy concentration in CeO 2 , which promotes the absorption of UV–visible light and the separation/transfer of electrons and holes, consequently elevating the catalytic activity. More importantly, through in - situ FT-IR, CO 2 adsorption/activation and the intermediates generated on catalyst surface during CO 2 photoreduction reaction were investigated and discussed in-depth. Similar carbonates and hydrocarbonates, such as HCO 3 −, b-CO 3 2− and m-CO 3 2−, have been found to be produced on CeO 2 and Ce M , while these intermediates accumulated and strongly covered on the catalyst surface have been revealed to be responsible for the gradually declined CO 2 reduction activity and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 19 Br 3 S 27 achieves high FE formate of 96% in a wide potential range of ∼ 700 mV. • Bi 19 Br 3 S 27 has been reconstructed to S,Br-comodified Bi during CO 2 RR. • S,Br-comodified Bi enhances the binding affinity towards CO 2 *- and HCOO*-. Electrocatalytic CO 2 reduction by renewable electricity is a promising approach to mitigate greenhouse effect and energy crisis, whereas the product selectivity and efficiency of catalysts remain to be significantly improved. Adjusting the electronic structure of catalysts by modulating the coordination environment of active sites is an effective way to improve their catalytic performance, but it is limited to deliberate doping. Herein, we synthesize Bi 19 Br 3 S 27 nanorod as an electrocatalyst for CO 2 reduction and realize the electronic structure modulation of Bi sites by S and Br comodification via an in-situ reconstruction. The as-obtained catalyst shows high Faradaic efficiency of formate (FE formate) of 98% at −1.1 V versus reversible hydrogen electrode (vs. RHE) and above 96% in a wide potential range of ∼ 700 mV (-1.1 V ∼ -1.8 V vs. RHE), superior to most of the reported catalysts. Meanwhile, a current density of about 150 mA cm−2 has been achieved in a flow cell with FE formate of 90%. It is disclosed that Bi 19 Br 3 S 27 has been reconstructed to S,Br-comodified Bi during CO 2 reduction process, resulting in positively charged Bi sites, which enhance the stability of CO 2 *- and HCOO*- intermediates and improve the catalytic activity towards formate formation. Compared with S-modified Bi and pure Bi, the S,Br-comodified Bi shows enhanced electron transfer rate and reaction kinetics, favoring its high efficiency in CO 2 RR. Ultimately, a maximum solar-to-formate conversion efficiency of ∼ 4.75% has been achieved in an electrolyzer integrating CO 2 RR and OER (O 2 evolution reaction) powered by Si solar cells. [ABSTRACT FROM AUTHOR]

A novel MnO 2 /g-C 3 N 4 heterojunction composite was synthesized via a simple in-situ redox reaction between KMnO 4 and MnSO 4 ·H 2 O adsorbed on the surface of g-C 3 N 4 for the first time. MnO 2 featuring 2D δ-phase layered structure was intimately attached onto the surface of g-C 3 N 4 layers via C O bonding. Notably, the synthesized MnO 2 /g-C 3 N 4 photocatalyst showed substantially enhanced photocatalytic activity in the reduction of CO 2 than pure g-C 3 N 4 and MnO 2 . The highest CO production amount of 9.6 μmol g −1 has been obtained at an optimized loading amount of MnO 2 under 1 h irradiation of a 300 W Xe lamp. The incorporation of narrow band gap MnO 2 on the surface of g-C 3 N 4 enhanced its light harvesting ability. And the solid hetero-interface between MnO 2 and g-C 3 N 4 together with their well matched band structure was favorable for the separation of photo-induced carriers, consequently enhanced its photocatalytic activity. This novel 2D-2D MnO 2 /g-C 3 N 4 heterostructure is expected to have great potentials in CO 2 photoreduction. [ABSTRACT FROM AUTHOR]