Final Report

The premise of this project was that coordination chemistry could be used to devise new kinds of microporous materials and that these materials could exhibit nanoscale porosity and selective chemical separation capabilities. Our initial materials focus was on aggregates of discrete hollow molecules, especially molecular squares. Subsequently our focus turned largely toward permanently microporous metal-organic frameworks (MOFs). Our approach emphasized coupling predictive & explanative computational modeling to materials design, synthesis, and property characterization

Glass-Encapsulated Light Harvesters: More Efficient Dye-Sensitized Solar Cells by Deposition of Self-Aligned, Conformal, and Self-Limited Silica Layers

A major loss mechanism in dye-sensitized solar cells (DSCs) is recombination at the $TiO_2$/electrolyte interface. Here we report a method to reduce greatly this loss mechanism. We deposit insulating and transparent silica $(SiO_2)$ onto the open areas of a nanoparticulate $TiO_2$ surface while avoiding any deposition of $SiO_2$ over or under the organic dye molecules. The $SiO_2$ coating covers the highly convoluted surface of the $TiO_2$ conformally and with a uniform thickness throughout the thousands of layers of nanoparticles. DSCs incorporating these selective and self-aligned $SiO_2$ layers achieved a 36% increase in relative efficiency versus control uncoated cells.Chemistry and Chemical Biolog

Atomic layer deposition of Pt@CsH_2PO_4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH_2PO_4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe_3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm^2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability

A metal-organic framework material that functions as an enantioselective catalyst for olefin epoxidation,” Chem. Commun

A new microporous metal-organic framework compound featuring chiral (salen)Mn struts is highly effective as an asymmetric catalyst for olefin epoxidation, yielding enantiomeric excesses that rival those of the free molecular analogue. Framework confinement of the manganese salen entity enhances catalyst stability, imparts substrate size selectivity, and permits catalyst separation and reuse. Crystalline metal-organic framework (MOF) compounds, especially those exhibiting zeolite-like properties such as high internal surface area and microporosity, comprise a promising emerging class of functional materials. 1 Among the functions most often envisioned is chemical catalysis. 2 The notion is that MOF-based catalysts may be able to replicate some of the key features of zeolitic catalysts (e.g. single-site reactivity, pore-defined substrate size and shape selectivity, easy catalyst separation and recovery, and catalyst recyclability) while incorporating reactivity and properties unique to molecular catalysts. One important property of many molecular catalysts that has yet to be demonstrated with purely zeolitic catalysts is enantioselectivity. Herein, we report that a microporous MOF containing chiral (salen)Mn struts is highly effective as an asymmetric catalyst for olefin epoxidation. The observed enantiomeric excesses (ee) rival those of the free molecular catalyst. At the same time, framework confinement enhances catalyst stability, imparts substrate size selectivity, and permits catalyst separation and reuse. 6 Since MOFs based exclusively upon metal-pyridine bonding tend to collapse if evacuated, L was incorporated instead in a more robust pillared paddlewheel structure, 1, containing pairs of zinc ions together with biphenyldicarboxylate (bpdc) as the second ligand. Notwithstanding the interpenetration, solvent occupies 57% of the volume of 1 as determined by PLATON. Notably, the ligands L of the paired networks are parallel to each other with cyclohexyl and tert-butyl groups protruding along the [100] direction. As such, the channel in the crystallographic b direction is essentially blocked, leaving distorted-rectangular and rhombic channels in the c and a directions with dimensions of 6.2 6 15.7 Å an

Water-stable zirconium-based metal-organic framework material with high-surface area and gas-storage capacities.

We designed, synthesized, and characterized a new Zr-based metal-organic framework material, NU-1100, with a pore volume of 1.53 ccg(-1) and Brunauer-Emmett-Teller (BET) surface area of 4020 m(2) g(-1) ; to our knowledge, currently the highest published for Zr-based MOFs. CH4 /CO2 /H2 adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g(-1) , which corresponds to 43 g L(-1) . The volumetric and gravimetric methane-storage capacities at 65 bar and 298 K are approximately 180 vSTP /v and 0.27 g g(-1) , respectively.OKF, JTH and RQS thank DOE ARPA-E and the Stanford Global Climate and Energy Project for support of work relevant to methane and CO2, respectively. TY acknowledges support by the U. S. Department of Energy through BES Grant No. DE-FG02-08ER46522. WB acknowledges support from the Foundation for Polish Science through the “Kolumb” Program. DFJ acknowledges the Royal Society (UK) for a University Research Fellowship. This material is based upon work supported by the National Science Foundation (grant CHE-1048773).This is the accepted manuscript. The final version is available as 'Water-Stable Zirconium-Based Metal–Organic Framework Material with High-Surface Area and Gas-Storage Capacities' from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/chem.201402895/abstract