Journal of Energy Chemistry, 2024

Molecular copper catalysts serve as exemplary models for correlating the structure-reaction-mechanism relationship in the electrochemical CO₂ reduction reaction (eCO₂R), owing to their adaptable environments surrounding the copper metal centres. This investigation, employing density functional theory (DFT) calculations, focuses on a novel family of binuclear Cu molecular catalysts. The modulation of their coordination configuration through the introduction of organic groups aims to assess their efficacy in converting CO₂ to C₂ products. Our findings highlight the crucial role of chemical valence state in shaping the characteristics of binuclear Cu catalysts, consequently influencing the eCO₂R behaviour. Notably, the Cu(II)Cu(II) macrocycle catalyst exhibits enhanced suppression of the hydrogen evolution reaction (HER), facilitating proton transfer and the eCO₂R process. Furthermore, we explore the impact of diverse electron-withdrawing and electron-donating groups coordinated to the macrocycle (R = –F, –H, and –OCH₃) on the electron distribution in the molecular catalysts. Strategic placement of –OCH₃ groups in the macrocycles leads to a favourable oxidation state of the Cu centres and subsequent C–C coupling to form C₂ products. This research provides fundamental insights into the design and optimization of binuclear Cu molecular catalysts for the electrochemical conversion of CO₂ to value-added C₂ products.

Cryst. Growth Des. 2023

Herein, we describe a series of molecular rotors formed by cocrystallizing three indolo[3,2-b]carbazole (ICZ) derivatives with butyl and cyclohexyl substituents, along with 1,4-diaza[2.2.2]bicyclooctane (DABCO). The structures of rotors I and III were confirmed through single-crystal X-ray diffraction (SCXRD), revealing a concatenated 1D arrangement between the two components. Variable-temperature (VT) SCXRD experiments on rotors I and III suggested that the rotator shows rotational motion, with activation energies of 6.8 and 1.8 kcal mol^–1, respectively. The lower activation energy for rotor III was attributed to the flexible environment around DABCO due to the presence of cyclohexyl groups, while the surroundings of rotor I were found to be more rigid. Additionally, our predictions of radiative and nonradiative decay constants indicate that the vibrations of the molecular rotors impact nonradiative decay rates and, consequently, the fluorescence quantum yields.

JPhys Energy 2021, 3 034005

Metal organic frameworks (MOFs) are promising photocatalytic materials due to their high surface area and tuneability of their electronic structure. We discuss here how to engineer the band structures and optical properties of a family of two-dimensional (2D) porphyrin-based MOFs, consisting of M tetrakis(4 carboxyphenyl)porphyrin structures (M TCPP, where M = Zn or Co) and metal (Co, Ni, Cu or Zn) paddlewheel clusters, with the aim of optimising their photocatalytic behaviour in solar fuel synthesis reactions (water splitting and/or CO2 reduction). Based on density functional theory (DFT) and time-dependent DFT simulations with a hybrid functional, we studied three types of composition/structural modifications: a) varying the metal centre at the paddlewheel or at the porphyrin centre to modify the band alignment; b) partially reducing the porphyrin unit to chlorin, which leads to stronger absorption of visible light; and c) substituting the benzene bridging between the porphyrin and paddlewheel, by ethyne or butadiyne bridges, with the aim of modifying the linker to metal charge transfer behaviour. Our work offers new insights on how to improve the photocatalytic behaviour of porphyrin- and paddlewheel-based MOFs.