Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

2021 ◽  
Author(s):  
Kevin Fabrizio ◽  
Konstantinos A. Lazarou ◽  
Lillian I. Payne ◽  
Liam P. Twight ◽  
Stephen Golledge ◽  
...  
Keyword(s):  
Band Gaps ◽  
Open Metal Sites ◽  
Earth Abundant

scholarly journals Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

2021 ◽  
Author(s):  
Kevin Fabrizio ◽  
Konstantinos Lazarou ◽  
Lillian Payne ◽  
Liam Twight ◽  
Christopher H. Hendon ◽  
...  
Keyword(s):  
Band Gaps ◽  
Redox Potentials ◽  
Research Attention ◽  
Co Catalysts ◽  
Redox Indicators ◽  
Open Metal Sites ◽  
Earth Abundant ◽  
Metal Organic ◽  
Electrostatic Control

<div> <div> <p>Titanium-based metal—organic frameworks (Ti-MOFs) attract intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers for co-catalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both charge storage and charge transfer depend on redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on co-catalysts rather than the intrinsic Ti reactivity in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd, Sr , and Ba ) or introduced to the pores (H, Li, Na, K) tune the electronic structure and band gaps of the MOFs. Through use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.</p> </div> </div>

scholarly journals Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

2021 ◽  
Author(s):  
Kevin Fabrizio ◽  
Konstantinos Lazarou ◽  
Lillian Payne ◽  
Liam Twight ◽  
Christopher H. Hendon ◽  
...  
Keyword(s):  
Band Gaps ◽  
Redox Potentials ◽  
Research Attention ◽  
Co Catalysts ◽  
Redox Indicators ◽  
Open Metal Sites ◽  
Earth Abundant ◽  
Metal Organic ◽  
Electrostatic Control

<div> <div> <p>Titanium-based metal—organic frameworks (Ti-MOFs) attract intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers for co-catalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both charge storage and charge transfer depend on redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on co-catalysts rather than the intrinsic Ti reactivity in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd, Sr , and Ba ) or introduced to the pores (H, Li, Na, K) tune the electronic structure and band gaps of the MOFs. Through use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.</p> </div> </div>

scholarly journals Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites

2021 ◽  
Author(s):  
Kevin Fabrizio ◽  
Konstantinos Lazarou ◽  
Lillian Payne ◽  
Liam Twight ◽  
Christopher H. Hendon ◽  
...  
Keyword(s):  
Band Gaps ◽  
Redox Potentials ◽  
Research Attention ◽  
Co Catalysts ◽  
Redox Indicators ◽  
Open Metal Sites ◽  
Earth Abundant ◽  
Metal Organic ◽  
Electrostatic Control

<div> <div> <div> <p>Titanium-based metal—organic frameworks (Ti-MOFs) attract intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers for co-catalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both charge storage and charge transfer depend on redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on co-catalysts rather than the intrinsic Ti reactivity in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis </p> <p>acidic cations installed in the MOF cluster (Cd, Sr , and Ba ) or introduced to the pores (H, Li, Na, K) tune the electronic structure and band gaps of the MOFs. Through use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.</p> </div> </div> </div>

Dynamic free energy surfaces for sodium diffusion in type II silicon clathrates

2016 ◽  
Vol 18 (7) ◽  
pp. 5121-5128 ◽  
Author(s):  
J. G. Slingsby ◽  
N. A. Rorrer ◽  
L. Krishna ◽  
E. S. Toberer ◽  
C. A. Koh ◽  
...  
Keyword(s):  
Free Energy ◽  
Wide Band ◽  
Band Gaps ◽  
Type Ii ◽  
Silicon Clathrates ◽  
Photovoltaic Materials ◽  
Earth Abundant ◽  
Energy Surfaces ◽  
Sodium Diffusion

Earth abundant semiconducting type II Si clathrates have attracted attention as photovoltaic materials due to their wide band gaps.

scholarly journals Polymorph engineering of CuMO2 (M = Al, Ga, Sc, Y) semiconductors for solar energy applications: from delafossite to wurtzite

2015 ◽  
Vol 71 (6) ◽  
pp. 702-706 ◽  
Author(s):  
David O. Scanlon ◽  
Aron Walsh
Keyword(s):  
Band Gaps ◽  
Underlying Structure ◽  
Structure Property ◽  
Conducting Oxides ◽  
Energy Applications ◽  
Structure Property Relationships ◽  
Earth Abundant ◽  
Chalcopyrite Lattice ◽  
Group 3 ◽  
The Difference

The cuprous oxide based ternary delafossite semiconductors have been well studied in the context of p-type transparent conducting oxides. CuAlO2, CuGaO2 and CuInO2 represent a homologous series where the electronic properties can be tuned over a large range. The optical transparency of these materials has been associated with dipole forbidden transitions, which are related to the linear O—Cu—O coordination motif. The recent demonstration that these materials can be synthesized in tetrahedral structures (wurtzite analogues of the chalcopyrite lattice) opens up a new vista of applications. We investigate the underlying structure–property relationships (for Group 3 and 13 metals), from the perspective of first-principles materials modelling, towards developing earth-abundant photoactive metal oxides. All materials studied possess indirect fundamental band gaps ranging from 1 to 2 eV, which are smaller than their delafossite counterparts, although in all cases the difference between direct and indirect band gaps is less than 0.03 eV.

Phonon Band Gaps

1997 ◽  
Vol 7 (3) ◽  
pp. 509-519 ◽  
Author(s):  
R. M. Hornreich ◽  
M. Kugler ◽  
S. Shtrikman ◽  
C. Sommers
Keyword(s):  
Band Gaps ◽  
Phonon Band

Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

2019 ◽  
Author(s):  
Andrew Rosen ◽  
M. Rasel Mian ◽  
Timur Islamoglu ◽  
Haoyuan Chen ◽  
Omar Farha ◽  
...  
Keyword(s):  
Density Functional ◽  
Metal Organic Frameworks ◽  
Redox Activity ◽  
Screening Methods ◽  
Bridging Ligands ◽  
Metal Centers ◽  
Computational Screening ◽  
Open Metal Sites ◽  
Metal Organic ◽  
Unsaturated Metal Sites

<p>Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O<sub>2</sub> and N<sub>2</sub> adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the O<sub>2</sub> adsorbate.</p>

Room Temperature Alkali Metal Reduction of Carbon Dioxide

2020 ◽  
Author(s):  
Lucas A. Freeman ◽  
Akachukwu D. Obi ◽  
Haleigh R. Machost ◽  
Andrew Molino ◽  
Asa W. Nichols ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Alkali Metals ◽  
Room Temperature ◽  
Chemical Reduction ◽  
Bond Cleavage ◽  
Open Shell ◽  
Metal Reduction ◽  
One Pot ◽  
Earth Abundant ◽  
Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO<sub>2</sub> to access useful CO<sub>2</sub>-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO<sub>2</sub> and the MGE. Herein we report the first successful chemical reduction of CO<sub>2</sub> at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO<sub>2</sub> adduct (<b>1</b>) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO<sub>2</sub>)]<sub>n</sub>(M = Li, Na, K, <b> 2</b>-<b>4</b>) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M<sub>2</sub>(CAAC–CO<sub>2</sub>)]<sub>n </sub>(<b>5</b>-<b>8</b>). It is notable that these crystalline clusters of reduced CO<sub>2</sub> may also be isolated via the “one-pot” reaction of free CO<sub>2</sub> with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products <b>2</b>-<b>8</b> were investigated using a combination of experimental and theoretical methods.<br>

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