We have developed a facile and scalable chemical reduction method assisted by microwave irradiation for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on the graphene sheets. The method allows rapid chemical reduction of exfoliated graphite oxide (GO) using a variety of reducing agents in either aqueous or organic media. It also allows the simultaneous reduction of GO and a variety of metal salts thus resulting in the dispersion of metallic and bimetallic nanoparticles supported on the large surface area of the thermally stable 2D graphene sheets.

This paper reports the development of a facile, general and effective approach, based on microwave irradiation (MWI), for the incorporation of a variety of metallic and bimetallic nanoparticle catalysts within the highly porous coordination polymer MIL-101. The current approach is based on the simultaneous activation of the pores of MIL-101 and the rapid chemical reduction of metal precursors using MWI in the presence of a reducing agent. Small Pd, Cu and Pd–Cu nanoparticles of 2–3 nm are incorporated within the pores and larger particles of 4–6 nm are supported on the surface of the MIL-101 crystals. TEM images reveal that the loading of the particles using MWI is uniform across the MIL crystals. The observed catalytic activities toward CO oxidation of the Pd nanocatalysts supported on the highly porous MIL-101 polymer are significantly higher than any other reported metal clusters supported on metal–organic frameworks. The observed high activity is attributed to the small metal nanoparticles imbedded within the pores of the MIL crystals. The activity of the small embedded particles is higher than those supported on the surface. This allows the use of small metal loadings for efficient low temperature CO oxidation. These results should allow optimization of a new class of nanocatalysts incorporated within the highly porous MIL-101. These materials are promising environmentally relevant catalyst systems.

Ultrasmall palladium nanoparticles (1.5–2.5 nm) encapsulated in metal–organic frameworks (MOFs) have been prepared by introducing a palladium precursor into a highly porous and hydrothermally stable amine-functionalized UiO-66 (NH₂-UiO-66) via a direct anionic exchange and subsequent H₂ reduction. The prepared Pd@NH₂-UiO-66 catalyst was then applied in the hydrodeoxygenation of vanillin (a typical model compound of lignin) at a low H₂ pressure in aqueous media. Excellent catalytic results (100% conversion of vanillin with exclusive selectivity for 2-methoxy-4-methylphenol) could be achieved over the developed 2.0 wt% Pd@NH₂-UiO-66 catalyst under mild conditions. Furthermore, the catalytic activity and selectivity were not affected after six reaction cycles indicating excellent stability and reproducibility of this catalyst system. It was found that the presence of free amine groups in the framework of NH₂-UiO-66 plays a key role in the formation of uniform, well-dispersed and leaching resistant palladium nanoparticles within the MOF host. Moreover, the developed Pd@NH₂-UiO-66 exhibits a novel synergetic catalysis in the hydrodeoxygenation due to the cooperation between the well-dispersed metallic Pd sites and the amine-functionalized MOF support, in which Pd offers hydrogenation activity and the MOF support facilitates hydrogenolysis of the intermediate vanillin alcohol to the 2-methoxy-4-methylphenol product.