Photocatalytic CO 2 reduction into formate (HCOO − ) has been widely studied with semiconductor and molecule-based systems, but it is rarely investigated with covalent organic frameworks (COFs). Herein, we report a novel donor−acceptor COF named Co-PI-COF composed of isoindigo and metallated porphyrin subunits that exhibits high catalytic efficiency (∼50 μmol formate g −1 h −1 ) at low-power visible-light irradiation and in the absence of rare metal cocatalysts. Density functional theory calculations and experimental diffusereflectance measurements are used to explain the origin of catalytic efficiency and the particularly low band gap (0.56 eV) in this material. The mechanism of photocatalysis is also studied experimentally and is found to involve electron transfer from the sacrificial agent to the excited Co-PI-COF. The observed high-efficiency conversion could be ascribed to the enhanced CO 2 adsorption on the coordinatively unsaturated cobalt centers, the narrow band gap, and the efficient transfer of the charge originating from the postsynthetic metallation. It is anticipated that this study will pave the way toward the design of new simple and efficient catalysts for photocatalytic CO 2 reduction into useful products.

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In this study, we investigated the surface thermodynamic properties of four MOF structures of the UiO-66 series, by employing seven molecular models, a thermal model, and three other methods using the inverse gas chromatography (IGC) technique at infinite dilution. We first determined the effect of the modulation of UiO-66 by an acid (e.g., formic acid and acetic acid) and on the other hand, we studied the effect of the functionalization of the organic linker by an amine group (NH2) on their dispersive component of the surface energy and on their Lewis acid–base properties. We found that all the studied MOFs presented an amphoteric character with a strong acidity whose acidity/basicity ratio is greater than 1 using all the models and methods in IGC. Moreover, the introduction of a modulator such as acetic acid or formic acid in the synthesis of these MOFs increased the number of structural defects and therefore increased the acidity of these MOFs. Similarly, the functionalization of the MOF by the NH2 group leads to an increase in the basicity constant of the functionalized MOF while remaining smaller than their acidity constant. In addition, the use of acids as modulators and amine groups as functional groups resulted in an increase in the dispersive component of the surface energy of the MOFs. Finally, comparing the results obtained by the different models and methods and based on the increasing order of the acidity of each MOF, it was clear that the thermal model resulted in more exact and precise values than the others. Our findings pave the way for the design and development of new acid catalysts based on UiO-66 structures.

Some Like It Hot: Geoffry A. Ozin and co‐workers demonstrate that the reverse water gas shift (RWGS) reaction, driven by a visible and near infrared responsive Pd@Nb2O5 is thermally activated with measured conversion rates as high as 1.8 mmol gcat−1 h−1, in article 1600189. Specifically, the RWGS reaction is enabled by heat generated from thermalization of photoexcited charge carriers in the Pd nanocrystals that function as “nanoheaters” for the entire Pd@Nb2O5 assembly, through non‐radiative relaxation of inter‐band and intra‐band conduction electron transitions. Overall this study advances our understanding of the underlying mechanism of photothermally driven CO2 reduction. Cover illustration by Chenxi Qian.