More Like this

1. Unraveling the origin of the “Turn-On” effect of Al-MIL-53-NO 2 during H 2 S detection

   https://doi.org/10.1039/C9CE01595G  

   Zhu, Zan ; He, Xiang ; Wang, Wei-Ning ( January 2020 , CrystEngComm)

   Nitro-functionalized metal–organic frameworks (MOFs), such as Al-MIL-53-NO 2 , have been widely used in quantitative hydrogen sulfide (H 2 S) detection based on the “turn-on” effect, where fluorescence enhancements were observed upon contact with H 2 S. This was believed to be caused by the fact that the electron-withdrawing –NO 2 groups in the initial non-luminescent MOFs were reduced to electron-donating –NH 2 groups in the sensing process. However, since most H 2 S detection is conducted in a suspension system consisting of MOFs and solvents, it is still unclear whether these –NH 2 groups are on MOFs or in the liquid. Using Al-MIL-53-NO 2 as a model MOF, this work aims to answer this question. Specifically, the supernatant and undissolved particles separated from the Al-MIL-53-NO 2 suspensions after being exposed to H 2 S were analyzed systematically. The results showed that it is the free BDC-NH 2 (2-aminobenzene-1,4-dicarboxylic acid) in the solution rather than the formation of Al-MIL-53-NH 2 that really caused the fluorescence enhancement. In particular, the formed BDC-NH 2 was reduced from the shedded BDC-NO 2 (2-nitrobenzene-1,4-dicarboxylic acid) during the decomposition of Al-MIL-53-NO 2 , which was attacked by OH − in the NaHS solution. We anticipate that this work will offer new ways of tracing fluorophores for MOF-based sensing applications in aqueous systems. 

   more » « less
2. Exceptional TcO 4 − sorption capacity and highly efficient ReO 4 − luminescence sensing by Zr 4+ MOFs

   https://doi.org/10.1039/c8ta07901c  

   Rapti, Sofia ; Diamantis, Stavros A. ; Dafnomili, Argyro ; Pournara, Anastasia ; Skliri, Euaggelia ; Armatas, Gerasimos S. ; Tsipis, Athanassios C. ; Spanopoulos, Ioannis ; Malliakas, Christos D. ; Kanatzidis, Mercouri G. ; et al ( October 2018 , Journal of Materials Chemistry A)

   The sorption properties of [Zr 6 O 4 (OH) 4 (NH 3 + -BDC) 6 ]Cl 6 · x H 2 O ( MOR-1 ) and H 16 [Zr 6 O 16 (H 2 PATP) 4 ]Cl 8 · x H 2 O ( MOR-2 ) towards ReO 4 − and TcO 4 − were studied in detail. Both MOR-1 and MOR-2 are very effective sorbents for ReO 4 − and TcO 4 − anions, with MOR-2 showing the highest sorption capacity (up to 4.1 ± 0.4 mmol g −1 ) among the known metal organic materials. Importantly, the exceptional sorption capacity of MOR-2 is retained even under conditions simulating acidic nuclear waste. In addition, MOR-1 and MOR-2 exhibit selective luminescence ReO 4 − sensing properties, demonstrated for the first time for MOF materials. 

   more » « less
3. Metal‐Organic Framework Derived Terephthalate Ligand Decorated TiO 2 with Various Morphologies for Efficient Photocatalytic H 2 Evolution

   https://doi.org/10.1002/chem.202203917  

   Dong, Pengyu ; Gao, Kangjie ; Li, Kang ; Wang, Haoyu ; Xi, Xinguo ; Feng, Pingyun ( March 2023 , Chemistry – A European Journal)

   It has been rarely reported the morphological control of derivatives of metal‐organic frameworks (MOFs) in hydrothermal conditions for photocatalytic applications. We report here a family of highly efficient composite photocatalysts composed of terephthalic acid/terephthalate (TPA) ligand and TiO₂with various morphologies (e. g., nanoparticles, nanosheets, and nanorods). The composites are synthesized by a simple one‐step hydrothermal method in various solvents (i. e., H₂O, HF, H₂SO₄, HCl, and HNO₃) using Ti‐based MOF (MIL‐125(Ti)) as precursor. The formation mechanism of composite materials with different morphological features is discussed. Impressively, the composite of TiO₂nanoparticles/TPA synthesized using H₂O as solvent under hydrothermal condition exhibits the highest photocatalytic H₂activity among the studied materials, with a photocatalytic H₂production rate of 6.38 mmol g⁻¹ h⁻¹, which is approximately 7.5‐fold higher than pure TiO₂(Degussa, P25) and prominent apparent quantum efficiency (AQE) of 65 % at 365 nm. Furthermore, the mechanism of boosted photocatalytic H₂production is discussed.

    

   more » « less
4. On the limit of proton-coupled electronic doping in a Ti( iv )-containing MOF

   https://doi.org/10.1039/d1sc03019a  

   Mancuso, Jenna L. ; Fabrizio, Kevin ; Brozek, Carl K. ; Hendon, Christopher H. ( September 2021 , Chemical Science)

   Ti IV -containing metal–organic frameworks are known to accumulate electrons in their conduction bands, accompanied by protons, when irradiated in the presence of alcohols. The archetypal system, MIL-125, was recently shown to reach a limit of 2e − per Ti 8 octomeric node. However, the origin of this limit and the broader applicability of this unique chemistry relies not only on the presence of Ti IV , but also access to inorganic inner-sphere Lewis basic anions in the MOF nodes. Here, we study the loading of protons and electrons in MIL-125, and assess the thermodynamic limit of doping these materials. We find that the limit is determined by the reduction potential of protons: in high charging regimes the MOF exceeds the H + /H 2 potential. Generally, we offer the design principle that inorganic anions in MOF nodes can host adatomic protons, which may stabilize meta-stable low valent transition metals. This approach highlights the unique chemistry afforded by MOFs built from inorganic clusters, and provides one avenue to developing novel catalytic scaffolds for hydrogen evolution and transfer hydrogenation. 

   more » « less
5. Phosphorus-based ligand effects on the structure and radical scavenging ability of molecular nanoparticles of CeO 2

   https://doi.org/10.1039/d1dt02667d  

   Russell-Webster, Bradley ; Lopez-Nieto, Javi ; Abboud, Khalil A. ; Christou, George ( November 2021 , Dalton Transactions)

   Two new Ce IV /O 2− clusters, (pyH) 8 [Ce 10 O 4 (OH) 4 (O 3 PPh) 12 (NO 3 ) 12 ] (1) and [Ce 6 O 4 (OH) 4 (O 2 PPh 2 ) 4 (O 2 C t Bu) 8 ] (2), have been prepared that contain P-based ligands for the first time. They were obtained from the reaction of (NH 4 ) 2 [Ce(NO 3 ) 6 ], PhPO 3 H 2 or Ph 2 PO 2 H, and t BuCO 2 H in a 2 : 1 : 2 molar ratio in pyridine/MeOH (10 : 1 mL). Both compounds contain a {Ce 6 O 4 (OH) 4 } face-capped octahedral core, with 1 containing an additional four Ce IV on the outside to give a supertetrahedral Ce 10 topology; the {Ce 6 O 8 } unit is the smallest recognizable fragment of the fluorite structure of CeO 2 . The HO˙ radical scavenging activities of 1 and 2 were measured by UV/vis spectral monitoring of methylene blue oxidation by HO˙ radicals in the presence and absence of the Ce/O clusters, and the results compared with those for larger Ce 24 and Ce 38 molecular nanoparticles of CeO 2 prepared in previous work. 1 and 2 are both very poor HO˙ radical scavengers compared with Ce 24 and Ce 38 , a result that is consistent with reports in the literature that PO 4 3− ions inhibit the radical scavenging ability of traditional CeO 2 nanoparticles and putatively assigned to PO 4 3− binding to the surface. 

   more » « less