Hierarchical surface-modification of nano-Cu toward one pot H-transfer-coupling-cyclization-CO2 fixation tandem reactions.

Fixation of CO2 into dihydroisobenzofuran derivatives has enormous applications in both production of natural products and antidepressant drugs, and reducing the green-house effect. However, the relatively complicated multi-step processes limit the further expansion of such a valuable CO2 conversion strategy. Herein, we hierarchically modify the surface of Cu nanoparticles (NPs) with Ag NPs and the robust metal-organic framework (MOF), ZIF-8, and report the presence of the Cu-Ag yolk-shell nanoalloy based heterogeneous catalysts, Cu@Ag and Cu@Ag@ZIF-8. The latter exhibits a crystalline "raisin bread" structure and specific synergic activity for catalyzing the tandem reactions of intra-molecular H-transfer, C-C and C-O coupling, cyclization, and carboxylation from CO2, leading to the first non-homogeneous preparation of dihydroisobenzofuran derivatives in high yield, selectivity, and recyclability under mild conditions. Theoretical calculations elucidate the tandem reaction pathway synergically catalyzed by Cu@Ag@ZIF-8, which offers insights for designing multiphase catalysts towards both organic synthesis and CO2 fixation through tandem processes in one pot.

The photocurrent response in the perovskite device based on coordination polymers: structure, topology, band gap and matched energy levels.

Using a rigid ditopic ligand, 4,5-di(4'-carboxylphenyl)benzene (H2L), three coordination polymers (CPs) formulated as MnL(H2O)2 (1), CdL(H2O) (2) and Mn2L2(DMF)3 (3) have been synthesized and structurally characterized by single-crystal X-ray diffraction. These three CPs display 2D architectures but with different topologies. The experimental data and DFT calculation indicate that CP 2 is a semiconductor, and its CB/VB energy levels match with those of the perovskite CH3NH3PbI3. A FTO/TiO2/CH3NH3PbI3/CP 2 device is fabricated and the CP-based device shows much larger photoresponse under visible light illumination (650 nm > λ > 350 nm, 100 mW cm-2) than the individual CP 2. At 0 V vs. AgCl/Ag, the largest photocurrent density yielded by the CP-based perovskite device is ca. 200 times that of CP 2, which is due to the matched energy levels of all the materials in the device, leading the photogenerated electron-hole pairs to be separated effectively. Meanwhile, the coverage of the insoluble CP on the surface of the perovskite CH3NH3PbI3 can improve the stability of the perovskite against water.