Single-step hydrogen production from NH3, CH4, and biogas in stacked proton ceramic reactors.

Proton ceramic reactors offer efficient extraction of hydrogen from ammonia, methane, and biogas by coupling endothermic reforming reactions with heat from electrochemical gas separation and compression. Preserving this efficiency in scale-up from cell to stack level poses challenges to the distribution of heat and gas flows and electric current throughout a robust functional design. Here, we demonstrate a 36-cell well-balanced reactor stack enabled by a new interconnect that achieves complete conversion of methane with more than 99% recovery to pressurized hydrogen, leaving a concentrated stream of carbon dioxide. Comparable cell performance was also achieved with ammonia, and the operation was confirmed at pressures exceeding 140 bars. The stacking of proton ceramic reactors into practical thermo-electrochemical devices demonstrates their potential in efficient hydrogen production.

Expanding the photoresponse of multidimensional hybrid lead bromide perovskites into the visible region by incorporation of subphthalocyanine.

This work explores a new methodology to adsorb a subphthalocyanine molecule (SubPc) on a hybrid lead bromide perovskite crystal structure with the aim of extending its photoresponse into the visible region. This process consists in the preparation of multidimensional 2D-3D perovskites. The use of large organic cations allows the possibility to insert guest molecules in the crystal structure of the perovskite. In this work, layered and 3D materials are obtained modifying the ratio of the organic cations (A/R) in the perovskite structure (RNH3)2An-1BnX3n+1. The present results show that incorporation of metal-free subphthalocyanine in the interlayer space provided by the 2D phase is a valid procedure to enhance the photoresponse of the perovskite solar cells.

Subphthalocyanine encapsulated within MIL-101(Cr)-NH2 as a solar light photoredox catalyst for dehalogenation of α-haloacetophenones.

Subphthalocyanine has been incorporated into a robust metal-organic framework having amino groups as binding sites. The resulting SubPc@MIL-101(Cr)-NH2 composite has a loading of 2 wt%. Adsorption of subphthalocyanine does not deteriorate host crystallinity, but decreases the surface area and porosity of MIL-101(Cr)-NH2. The resulting SubPc@MIL-101(Cr)-NH2 composite exhibits a 575 nm absorption band responsible for the observed photoredox catalytic activity under simulated sunlight irradiation for hydrogenative dehalogenation of α-haloacetophenones and for the coupling of α-bromoacetophenone and styrene. The material undergoes a slight deactivation upon reuse. In comparison to the case of phthalocyanines the present study is one of the few cases showing the use of subphthalocyanine as a photoredox catalyst, with its activity derived from site isolation within the MOF cavities.

Design of cost-efficient and photocatalytically active Zn-based MOFs decorated with Cu2O nanoparticles for CO2 methanation.

Here we show for the first time a MOF that is photocatalytically active for light-assisted CO2 methanation under mild conditions (215 °C) without the inclusion of metallic nanoparticles or any sacrificial agent. The presence of Cu2O nanoparticles causes a 50% increase in the photocatalytic activity. This result paves the way for developing efficient and cost-effective materials for CO2 elimination.

Electronic Energy Transfer in a Subphthalocyanine-Zn Porphyrin Dimer Studied by Linear and Nonlinear Ultrafast Spectroscopy.

The efficient harvesting and transport of visible light by electronic energy transfer (EET) are critical to solar energy conversion in both nature and molecular electronics. In this work, we study EET in a synthetic dyad comprising a visible absorbing subphthalocyanine (SubPc) donor and a Zn tetraphenyl porphyrin (ZnTPP) acceptor. Energy transfer is probed by steady-state spectroscopy, ultrafast transient absorption, and two-dimensional electronic spectroscopy. Steady-state and time-resolved experiments point to only weak electronic coupling between the components of the dimer. The weak coupling supports energy transfer from the SubPc to the zinc porphyrin in 7 ps, which itself subsequently undergoes intersystem crossing to populate the triplet state. The rate of the forward energy transfer is discussed in terms of the structure of the dimer, which is calculated by density functional theory. There is evidence of back energy transfer from the ZnTPP on the hundreds of picoseconds time scale. Sub-picosecond spectral diffusion was also observed and characterized, but it does not influence the picosecond energy transfer.

Synthesis of Porphyrin-CdSe Quantum Dot Assemblies: Controlling Ligand Binding by Substituent Effects.

Cadmium selenide quantum dots of 2.2-2.3 nm diameter were prepared by phosphorus-free methods using oleic acid as stabilizing surface ligand. Ligand exchange monitored quantitatively by (1)H NMR spectroscopy gave an estimate of 30-38 monodentate ligands per nanocrystal, with a ligand density of 1.8-2.3 nm(-2). The extent of ligand exchange with macrocycles carrying one or more functional groups was investigated, with the aim of producing nanocrystal-macrocycle conjugates with a limited number of coligands. Metal-free porphyrins are able to sequester the Cd(2+) ions from the Cd(oleate)2 outer layer of the nanocrystals. Zinc porphyrin complexes carrying one carboxylate function displace oleate efficiently to give porphyrin/CdSe composites with porphyrins stacked upright on the crystal surface. Porphyrins with four potential ligating sites are able to bind to the crystal surface only if the donors are at the end of sufficiently long and flexible tethers. High-dilution methods allowed the synthesis and isolation of well-defined composites of composition [CdSe{porphyrin}2], where porphyrin = 5,10,15,20-tetrakis{3-(carboxy-n-alkyloxy)phenyl}porphyrinato zinc (n = 5 or 10) and 5,10,15,20-tetrakis{3-(11-undecenyloxythiol)phenyl}porphyrinato zinc. Comparison of the composition data obtained by (1)H NMR spectroscopy with luminescence quenching behavior suggests a dependence of quenching efficiency on the tether length. Luminescence quenching was also observed for porphyrins that, according to (1)H NMR results, do not undergo surface ligand exchange.

A π-Extended Donor-Acceptor-Donor Triphenylene Twin Linked via a Pyrazine Bridge.

ß-Amino triphenylenes can be accessed via palladium catalyzed amination of the corresponding triflate using benzophenone imine. Transformation of amine 6 to benzoyl amide 18 is also straightforward, and its wide mesophase range demonstrates that the new linkage supports columnar liquid crystal formation. Amine 6 also undergoes clean aerobic oxidation to give a new twinned structure linked through an electron-poor pyrazine ring. The new discotic liquid crystal motif contains donor and acceptor fragments and is more oval in shape rather than disk-like. It forms a wide range columnar mesophase. Absorption spectra are strong and broad; emission is also broad and occurs with a Stokes shift of ca. 0.7 eV, indicative of charge-transfer character.

Synthesis of meso-substituted subphthalocyanine-subporphyrin hybrids: boron subtribenzodiazaporphyrins.

The first syntheses of hybrid structures that lie between subphthalocyanines and subporphyrins are reported. The versatile single-step synthetic method uses a preformed aminoisoindolene to provide the bridging methine unit and its substituent while trialkoxyborates simultaneously act as Lewis acid, template, and provider of the apical substituent. The selection of each component therefore allows for the controlled formation of diverse, differentially functionalized systems. The new hybrids are isolated as robust, pure materials that display intense absorption and emission in the mid-visible region. The new compounds are further characterized in solution and solid state by variable-temperature NMR spectroscopy and X-ray crystallography, respectively.