skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 5:00 PM ET until 11:00 PM ET on Friday, June 21 due to maintenance. We apologize for the inconvenience.


Title: Charge‐Separated and Lewis Paired Metal–Organic Framework for Anion Exchange and CO 2 Chemical Fixation
Abstract

Charge‐separated metal–organic frameworks (MOFs) are a unique class of MOFs that can possess added properties originating from the exposed ionic species. A new charge‐separated MOF, namely, UNM‐6 synthesized from a tetrahedral borate ligand and Co2+cation is reported herein. UNM‐6 crystalizes into the highly symmetricP43nspace group with fourfold interpenetration, despite the stoichiometric imbalance between the B and Co atoms, which also leads to loosely bound NO3anions within the crystal structure. These NO3ions can be quantitatively exchanged with various other anions, leading to Lewis acid (Co2+) and Lewis base (anions) pairs within the pores and potentially cooperative catalytic activities. For example, UNM‐6‐Br, the MOF after anion exchange with Branions, displays high catalytic activity and stability in reactions of CO2chemical fixation into cyclic carbonates.

 
more » « less
Award ID(s):
1904659 2101535
NSF-PAR ID:
10256340
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Chemistry – A European Journal
Volume:
26
Issue:
61
ISSN:
0947-6539
Page Range / eLocation ID:
p. 13788-13791
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Traditional MOF e‐CRR, constructed from catalytic linkers, manifest a kinetic bottleneck during their multi‐electron activation. Decoupling catalysis and charge transport can address such issues. Here, we build two MOF/e‐CRR systems, CoPc@NU‐1000 and TPP(Co)@NU‐1000, by installing cobalt metalated phthalocyanine and tetraphenylporphyrin electrocatalysts within the redox active NU‐1000 MOF. For CoPc@NU‐1000, the e‐CRR responsive CoI/0potential is close to that of NU‐1000 reduction compared to the TPP(Co)@NU‐1000. Efficient charge delivery, defined by a higher diffusion (Dhop=4.1×10−12 cm2 s−1) and low charge‐transport resistance (=59.5 Ω) in CoPC@NU‐1000 led FECO=80 %. In contrast, TPP(Co)@NU‐1000 fared a poor FECO=24 % (Dhop=1.4×10−12 cm2 s−1and=91.4 Ω). For such a decoupling strategy, careful choice of the host framework is critical in pairing up with the underlying electrochemical properties of the catalysts to facilitate the charge delivery for its activation.

     
    more » « less
  2. Abstract

    Traditional MOF e‐CRR, constructed from catalytic linkers, manifest a kinetic bottleneck during their multi‐electron activation. Decoupling catalysis and charge transport can address such issues. Here, we build two MOF/e‐CRR systems, CoPc@NU‐1000 and TPP(Co)@NU‐1000, by installing cobalt metalated phthalocyanine and tetraphenylporphyrin electrocatalysts within the redox active NU‐1000 MOF. For CoPc@NU‐1000, the e‐CRR responsive CoI/0potential is close to that of NU‐1000 reduction compared to the TPP(Co)@NU‐1000. Efficient charge delivery, defined by a higher diffusion (Dhop=4.1×10−12 cm2 s−1) and low charge‐transport resistance (=59.5 Ω) in CoPC@NU‐1000 led FECO=80 %. In contrast, TPP(Co)@NU‐1000 fared a poor FECO=24 % (Dhop=1.4×10−12 cm2 s−1and=91.4 Ω). For such a decoupling strategy, careful choice of the host framework is critical in pairing up with the underlying electrochemical properties of the catalysts to facilitate the charge delivery for its activation.

     
    more » « less
  3. Abstract

    Metal–organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)‐based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO2reduction reaction (CO2RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm−2at −0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s−1. In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state‐of‐the‐art MOF and MOF‐derived catalysts, respectively. The operando Cu K‐edge X‐ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu+) during CO2RR which reversibly returns to Cu2+after the reaction. The outstanding CO2catalytic functionality of conductive MOFs (c‐MOFs) can open a way toward high‐energy‐density electrochemical systems.

     
    more » « less
  4. Abstract

    Cooperative cluster metalation and ligand migration were performed on a Zr‐MOF, leading to the isolation of unique bimetallic MOFs based on decanuclear Zr6M4(M=Ni, Co) clusters. The M2+reacts with the μ3‐OH and terminal H2O ligands on an 8‐connected [Zr6O4(OH)8(H2O)4] cluster to form a bimetallic [Zr6M4O8(OH)8(H2O)8] cluster. Along with the metalation of Zr6cluster, ligand migration is observed in which a Zr–carboxylate bond dissociates to form a M–carboxylate bond. Single‐crystal to single‐crystal transformation is realized so that snapshots for cooperative cluster metalation and ligand migration processes are captured by successive single‐crystal X‐ray structures. In3+was metalated into the same Zr‐MOF which showed excellent catalytic activity in the acetaldehyde cyclotrimerization reaction. This work not only provides a powerful tool to functionalize Zr‐MOFs with other metals, but also structurally elucidates the formation mechanism of the resulting heterometallic MOFs.

     
    more » « less
  5. Abstract

    Metal‐Organic Frameworks (MOFs) recently emerged as a new platform for the realization of integrated devices for artificial photosynthesis. However, there remain few demonstrations of rational tuning of such devices for improved performance. Here, a fast molecular water oxidation catalyst working via water nucleophilic attack is integrated into the MOF MIL‐142, wherein Fe3O nodes absorb visible light, leading to charge separation. Materials are characterized by a range of structural and spectroscopic techniques. New, [Ru(tpy)(Qc)(H2O)]+(tpy = 2,2′:6′,2″‐terpyridine and Qc = 8‐quinolinecarboxylate)‐doped Fe MIL‐142 achieved a high photocurrent (1.6 × 10−3A·cm−2) in photo‐electrocatalytic water splitting at pH = 1. Unassisted photocatalytic H2evolution is also reported with Pt as the co‐catalyst (4.8 µmol g−1min−1). The high activity of this new system enables hydrogen gas capture from an easy‐to‐manufacture, scaled‐up prototype utilizing MOF deposited on FTO glass as a photoanode. These findings provide insights for the development of MOF‐based light‐driven water‐splitting assemblies utilizing a minimal amount of precious metals and Fe‐based photosensitizers.

     
    more » « less