The poor stability of metal-organic frameworks (MOFs) severely limits their catalytic applications. The in-situ activation of stable MOFs catalyst not only simplifies the catalytic process, but also reduces the energy....
It is challenging to synthesize a stable ultrafine Pd catalyst with high selectivity and activity at low temperatures toward hydrogenation of furfural (FF). We report an approach of applying C�N and S−O entities in a highly stable La metal− organic framework (La-MOF) (LaQS) as the platform support that confines Pd nanoparticles (NPs) through coordination, resulting in a stable Pd/LaQS catalytic system. The catalytic conversion of FF into tetrahydrofurfuryl alcohol (THFA) using this catalyst can be done as simply as one-step hydrogenation at room temperature, with a high selectivity of >99% maintained even at 120 °C. The outstanding catalytic activity and selectivity are mainly attributed to the electronic effect of metal−support in Pd/ LaQS, which produces electron-rich Pd and enhanced Lewis-acid LaQS. Especially, this electronic effect can be facilely tuned by the Pd loading in Pd/LaQS. On the one hand, electron-rich ultrafine Pd promotes the activation of H 2 and improves the reaction activity. On the other hand, the acid-enhanced LaQS support not only promotes the activation of FF and improves its activity, but also the positive electricity of the LaQS support is conducive to the reactant adsorption and product desorption, thus improving the THFA selectivity. This work develops a stable LaQS support for the stabilization of ultrafine metal nanoparticles via the metal−support interaction for enhanced catalysis, which sheds light on the construction of efficient MOF-based catalysts for task-specific applications.
The development of high-content non-noble metal nanocatalysts
is
important for multiphase catalysis applications. However, it is a
challenge to solve the agglomeration in the preparation of high-content
metal catalysts. In this paper, a carbon-based catalyst (Co@CN-G-600)
with 71.28 wt % cobalt metal content was prepared using a new strategy
of gas-phase carbon coating assisted by glycerol. The core of this
strategy is to maintain the spacing of metallic cobalt by continuous
replenishment of dissociated ligands during pyrolysis over gas-phase
glycerol. This approach is also applicable to other non-noble metals.
When Co@CN-G-600 was further used as a catalyst for the selective
hydrogenation of furfural (FF) to prepare furfuryl alcohol (FOL),
the yield of FOL was >99.9% under mild conditions of 80 °C,
compared
to only 8.23% catalytic yield at up to 130 °C for Co@CN-600 without
glycerol. The excellent catalytic performance mainly lies in the fact
that the introduction of glycerol modulates the size effect, electronic
effect, and acidic site intensity of the high-content Co catalyst,
which promotes the activation of FF and hydrogen. Meanwhile, the optimized
specific surface area and pore structure by glycerol improve the accessibility
of high-density active sites and promote more efficient mass transfer.
In addition, the introduction of glycerol produced a graphitic carbon
layer encapsulation structure relative to Co@CN-600, which substantially
improved the cycling stability of the catalyst. This study resolves
the paradox of high content and high dispersion of non-noble metal
catalysts in the synthesis process and provides a general pathway
and example for the preparation of stable high-content metal catalysts.
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