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Developing a highly active, acid-resistant and low-cost catalyst which can perform well in aqueous solution has long been sought for practical and sustainable lignocellulosic biomass transformation. In this work, a series of Ce–P–Co heterogeneous catalysts were prepared by a convenient solvothermal method for catalytic hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) in water. By comprehensive characterizations and catalytic measurements, the structure of the prepared Ce–P–Co samples was disclosed as (CePO4)m/Co2P composites with a modulated molar ratio (m) of 0.04–0.34. With the introduction of CePO4, the unique hydrogen activation on CePO4 markedly accelerated the reaction, with the GVL yield after 90 min on (CePO4)m/Co2P (45–97%) being much higher than on pure Co2P (26%), together with an attractive TOF of 0.27–0.61 s−1 on (CePO4)m/Co2P (comparable to precious metal catalysts). Further analysis of the kinetic and acidic features indicated a Langmuir–Hinshelwood mechanism, initiated by activation of H2 and LA on CePO4 and Co2P, respectively, followed by a surface reaction of the two activated species as the rate-determining step, as a plausible pathway for producing GVL from LA on (CePO4)m/Co2P. The consistent catalytic performance during recycling tests and the unchanged morphological, bulk and surface structure features of the used catalyst relative to the fresh catalyst confirmed that the (CePO4)m/Co2P structure was robust enough to endure the acidic aqueous environment for efficiently and sustainably converting LA to GVL. The advantages of high catalytic efficiency, stable, acid-resistant structure and low cost marked (CePO4)m/Co2P as a competitive and practical heterogeneous catalyst for sustainable, scaled-up lignocellulosic biomass transformation. [ABSTRACT FROM AUTHOR]

The nanocomposites of Co nanoparticles with composition-adjustable Co X N composited on surface in carbon coverage (Co@Co x N@C) were feasibly prepared upon a dual-ligand MOF manipulating strategy, the highly dispersed Co x N on Co matrix was quite efficient for activating C O and lowering the reaction activation energy (Ea), leading to the superior TOF and yield for selective hydrogenation of citral to nerol and geraniol. • Efficient and stable Co@Co x N@C nanocomposite catalysts for citral hydrogenation were feasibly acquired from a dual-ligand-MOF manipulating strategy. • The composition of exposed Co x N could be conveniently adjusted from the strategy. Interstitial compounds with tunable surface properties are highly desirable for advanced applications. Here, we present a dual-ligand-metal-organic framework (MOF) strategy to synthesize Co N C catalysts for the selective hydrogenation of citral. The dual-ligand MOF was synthesized by coordinating Co with both a N-donor ligand and a benzenedicarboxylic acid ligand, and calcining in a N 2 atmosphere at 973, 1073, or 1173 K. The Co N C catalysts derived from this strategy were Co nanoparticles (10.0–20.0 nm in diameter) with composite Co/Co x N surfaces covered in a layer of carbon (Co@Co x N@C). The highest Co x N surface composition, 0.54, was achieved when the precursor was calcined at 1073 K; this catalyst exhibited 100% citral conversion with 98% selectivity for the desired products (up to 60% selectivity for the most valuable C O hydrogenation product) and a superior turnover frequency (TOF) of 0.56 s−1. In-situ IR spectra and kinetic investigations were used to confirm that the exposed Co x N on the Co@CoxN@C nanostructures contributed to activating the C O bond and facilitating the transformation of citral to the desired C O hydrogenation products. The results of this study suggest that this dual-ligand-MOF strategy could be used to construct efficient interstitial compounds for advanced applications. [ABSTRACT FROM AUTHOR]