xPd100-xCu/UiO-66-NH2 catalysts for selective 5-hydroxymethylfurfural reduction

The present work is focused on a strategy to regulate the properties of monometallic Pd and bimetallic PdCu catalysts for selective 5-hydroxymethylfurfural (HMF) reduction via the interaction with the functional groups of the NH2-modified Zr-based metal-organic frameworks (Zr-MOFs). xPd100-xCu/UiO-66-NH2-X catalysts with different fractions of amino terephthalate linkers as well as Pd and Cu metals (x and 100-x, respectively) in bimetallic composition are prepared with impregnation reduction technique. The obtained samples are studied using a complex of methods, including XRD, low-temperature nitrogen adsorption, IR spectroscopy, and CO pulsed chemisorption. The effect of NH2 groups on the adsorption properties of the Zr-MOFs towards Pd and Cu precursors and on Pd and PdCu species formation in xPd100-xCu/UiO-66-NH2-X catalysts is considered. The formation of active particles at various stages of catalyst formation is studied in detail. 50 % fraction of NH2 linkers is found optimal for the formation of active and selective mono- and bimetallic CuPd catalysts, while 100 % fraction significantly reduces the activity of the samples due to the strong interaction of active Pd species with the support and does not allow the formation of bimetallic catalysts. [Display omitted] •Metal precursor interaction with NH2 groups is crucial for xPd1-xCu species formation.•50 % NH2 linkers fraction is optimal for xPd100-xCu@UiO-66-NH2 catalyst formation.•100 % NH2 linkers fraction does not allow formation of bimetallic xPd1-xCu species.