Recently, a large number of nanostructured metal-containing materials have been developed for the electrochemical CO 2 reduction reaction (eCO 2 RR). However, it remains a challenge to achieve high activity and selectivity with respect to the metal load due to the limited concentration of surface metal atoms. Here, it is reported that the bismuth-based metal-organic framework Bi(1,3,5-tris(4-carboxyphenyl)benzene), herein denoted Bi(btb), works as a precatalyst and undergoes a structural rearrangement at reducing potentials to form highly active and selective catalytic Bi-based nanoparticles dispersed in a porous organic matrix. The structural change is investigated by electron microscopy, X-ray diffraction, total scattering, and spectroscopic techniques. Due to the periodic arrangement of Bi cations in highly porous Bi(btb), the in situ formed Bi nanoparticles are well-dispersed and hence highly exposed for surface catalytic reactions. As a result, high selectivity over a broad potential range in the eCO 2 RR toward formate production with a Faradaic efficiency up to 95(3)% is achieved. Moreover, a large current density with respect to the Bi load, i.e., a mass activity, up to 261(13) A g −1 is achieved, thereby outperforming most other nanostructured Bi materials.
Photocatalytic organic conversions involving a hydrogen transfer (HT) step have attracted much attention, but the efficiency and selectivity under visible light irradiation still needs to be significantly enhanced. Here we have developed a noble metal-free, basic-site engineered bismuth oxybromide [Bi 24 O 31 Br 10 (OH) δ ] that can accelerate the photocatalytic HT step in both reduction and oxidation reactions, i.e., nitrobenzene to azo/azoxybenzene, quinones to quinols, thiones to thiols, and alcohols to ketones under visible light irradiation and ambient conditions. Remarkably, quantum efficiencies of 42% and 32% for the nitrobenzene reduction can be reached under 410 and 450 nm irradiation, respectively. The Bi 24 O 31 Br 10 (OH) δ photocatalyst also exhibits excellent performance in up-scaling and stability under visible light and even solar irradiation, revealing economic potential for industrial applications.
Palladium-metalated
PCN-222 enables the aerobic photo-oxidative
cross-condensation of anilines with benzylic amines yielding a series
of linear and cyclic imines. The reaction is very efficient under
mild conditions, which allows the isolation of simple, yet elusive,
intermediates such as 2-(benzylideneamino)aniline and 2-(benzylideneamino)phenols.
Recyclability studies show excellent activity and selectivity after
five runs. The methodology was successfully applied for the synthesis
of an antitumor agent (PMX-610).
The crystalline two-dimensional thiostannate Sn3S7(trenH)2 [tren = tris(2-aminoethyl)amine] consists of negatively charged (Sn3S72−)n polymeric sheets with trenH+ molecular species embedded in-between. The semiconducting compound is a violet light absorber with a band gap of 3.0 eV. In this study the compound was synthesized and functionalized by introducing the cationic dyes Methylene Blue (MB) or Safranin T (ST) into the crystal structure by ion exchange. Dye capacities up to approximately 45 mg/g were obtained, leading to major changes of the light absorption properties of the dye stained material. Light absorption was observed in the entire visible light region from red to violet, the red light absorption becoming more substantial with increasing dye content. The ion exchange reaction was followed in detail by variation of solvent, temperature and dye concentration. Time-resolved studies show that the ion exchange follows pseudo-second order kinetics and a Langmuir adsorption mechanism. The pristine and dye stained compounds were characterized by powder X-ray diffraction and scanning electron microscopy revealing that the honeycomb hexagonal pore structure of the host material was maintained by performing the ion exchange in the polar organic solvent acetonitrile, while reactions in water caused a break-down of the long-range ordered structure.
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