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1.
ACS Cent Sci ; 9(1): 27-35, 2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36712491

RESUMO

Metal-organic frameworks (MOFs) with Brønsted acidity are an alternative solid acid catalyst for many important chemical and fuel processes. However, the nature of the Brønsted acidity on the MOF's metal cluster or center is underexplored. To design and optimize the acid strength and density in these MOFs, it is important to understand the origin of their acidity at the molecular level. In the present work, isoreticular MOFs, ZrNDI and HfNDI (NDI = N,N'-bis(5-isophthalate)naphthalenediimide), were prepared as a prototypical system to unravel and compare their Brønsted and Lewis acid sites through an array of spectroscopic, computational, and catalytic characterization techniques. With the aid of solid-state nuclear magnetic resonance and density functional calculations, Hf6 oxo-clusters on HfNDI are quantitatively proved to possess a higher density Brønsted acid site, while ZrNDI-based MOFs display stronger and higher-population Lewis acidity. HfNDI-based MOFs exhibit a superior catalytic performance in activating dihydroxyacetone (DHA) and converting DHA to ethyl lactate, with 71.1% selectivity at 54.7% conversion after 6 h. The turnover frequency of BAS-dominated Hf-MOF in DHA conversion is over 50 times higher than that of ZSM-5, a strong BAS-based zeolite. It is worth noting that HfNDI is reported for the first time in the literature, which is an alternative platform catalyst for biorefining and green chemistry. The present study furthermore highlights the uniqueness of Hf-based MOFs in this important biomass-to-chemical transformation.

2.
Chem Commun (Camb) ; 55(30): 4419-4422, 2019 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-30916077

RESUMO

We designed a composite of carbon quantum dots (CQDs) with a carbon layer (CL) covering Cu2O nanocatalysts (CL@CQDs/Cu2O), which exhibited better photocatalytic performance than pure Cu2O and CQDs/Cu2O particles with good stability and efficiency for CO2 conversion.

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