Metal–organic frameworks (MOFs) have emerged as an exciting class of porous materials that can be structurally designed by choosing particular components according to desired applications. Despite the wide interest in and many potential applications of MOFs, such as in gas storage, catalysis, sensing and drug delivery, electrical semiconductivity and its control is still rare. The use and fabrication of electronic devices with MOF-based components has not been widely explored, despite significant progress of these components made in recent years. Here we report the synthesis and properties of a new highly crystalline, electrochemically active, cobalt and naphthalene diimide-based MOF that is an efficient electrical semiconductor and has a broad absorption spectrum, from 300 to 2500 nm. Its semiconductivity was determined by direct voltage bias using a four-point device, and it features a wavelength dependant photoconductive–photoresistive dual behaviour, with a very high responsivity of 2.5 × 105 A W−1.

No abstract

Under visible light irradiation [Cr(ttpy)2]3+ can be reduced twice by a tertiary amine; the photoreduction processes are accelerated in the presence of [Ru(bpy)3]2+ acting as an antenna thanks to an efficient electron transfer reaction from [Ru(bpy)3]2+* to [Cr(ttpy)2]3+.

Under visible irradiation in DMF/TEOA, the hybrid nanomaterial Ru(ii)/TiO2/Mn(i), lead to the selective reduction of CO2 into HCOO−.

We propose in this work a stepwise approach to construct photoelectrodes. This takes advantage of the self-assembly interactions between thiol with a gold surface and terpyridine ligands with first-row transition metals. Here, a [Ru(bpy)] photosensitive center bearing a free terpyridine group has been used to construct two linear dyads on gold (Au/[Zn-Ru] and Au/[Co-Ru]). The stepwise construction was characterized by electrochemistry, quartz crystal microbalance, and atomic force microscopy imaging. The results show that the dyads behave as rigid layers and are inhomogeneously distributed on the surface. The surface coverages are estimated to be in the order of 10 mol cm. The kinetics of the heterogeneous electron transfer is determined on modified gold ball microelectrodes using Laviron's formula. The oxidation rates of the terminal Ru(II) subunits are estimated to be 700 and 2300 s for Au/[Zn-Ru] and Au/[Co-Ru], respectively. In the latter case, the rate is limited by the kinetics of electron transfer between an intermediate Co(II) center and the gold surface. For Au/[Zn-Ru], the Zn-bis-terpyridine center is not involved in the electron-transfer process and the oxidation of the Ru(II) subunit occurs through a superexchange process. In the presence of a tertiary amine in solution, the electrodes at a bias of 0.12 V behave as photoanodes when subjected to visible light irradiation. The magnitude of the photocurrent is around 10 μA cm for Au/[Co-Ru] and 5 μA cm for Au/[Zn-Ru], proving the importance of an electron relay on the photon-to-current conversion. The results suggest an efficient conversion for Au/[Co-Ru], since each bound dyad, once excited, injects an electron around 10 times per second.

Herein we report the synthesis and electrochemical and photophysical behaviors of a nanocomposite TiO 2 /P-[Rupyr] 2+ , where [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) cores bearing two pyrrole substituents on distinct bipyridines and a phosphonic anchoring group on the third bipyridine are immobilized on TiO 2 colloidal nanoparticles. Under visible light and in the presence of O 2 as a sacrificial electron scavenger, TiO 2 /P-[Ru-pyr] 2+ was converted into a suprastructure TiO 2 /P-oligo(Ru-pyr), where the [Ru(bpy) 3 ] 2+ cores were linked together through a pyrrole coupling reaction. The photoinduced charge separated state (e − )TiO 2 / Ru II -pyr + was revealed by electron paramagnetic resonance (EPR) spectroscopy ((e − )TiO 2 signal). The oxidative coupling of pyrroles was ascertained by identifying the additional organic radical EPR signal with DFT calculations of pyrrole-derived oligomers, combined with X-ray photoelectron spectroscopy (XPS) results. TiO 2 /P-oligo(Ru-pyr) exhibited a higher rate of electron injection from [Ru(bpy) 3 ] 2+ * to TiO 2 than for colloidal nanoparticules without pyrrole denoted as TiO 2 /P-[Ru] 2+ . The composites were then electrophoretically deposited on a fluorine-doped tin oxide surface and tested as photoanodes. At a bias of 0.12 V vs Ag/Ag + 0.01 M, FTO/TiO 2 /P-oligo(Ru-pyr) in the presence of tertiary amine as a sacrificial electron donor, displayed a current density double that of FTO/TiO 2 /P-[Ru] 2+ under similar conditions. XPS confirmed the stability of [Ru(bpy) 3 ] 2+ cores after the photopolymerization process, but a partial desorption was observed after the electrophoretic deposition.

Visible light-driven conversion of CO 2 into more value-added products is a promising technology not only for diminution of CO 2 emission but also for solar energy storage in the form of chemical energy. However, photocatalytic materials that can efficiently and selectively reduce CO 2 -to-CO in a fully aqueous solution typically involve precious metals that limit their suitability for large scale applications. Herein, a novel photocatalytic assembly is reported, consisting of polymeric carbon nitride quantum dots (CNQDs) as the visible light absorber and a Fe-porphyrin complex (Fe-p-TMA) as the catalyst for CO 2 -to-CO conversion. Both components were carefully selected to allow for excellent solubility in water as well as improved electronic communication through complementary electrostatic and π-π interactions. This CNQD • [Fe-p-TMA] hybrid assembly, at the optimized molar ratio, can produce CO with a turnover number (TON) exceeding 10 5 and selectivity ~96 % after 10 hours of visible light irradiation (400-700 nm). It is postulated that the enhanced CO 2 -to-CO transformation performance is due to the convenience of a more direct charge transfer (CT) pathway between the CNQDs and [Fe-p-TMA] motif.