Surpassing nature: A hybrid catalyst in which Candida antarctica lipase B and a nanopalladium species are co‐immobilized into the compartments of mesoporous silica is presented. The metal nanoparticles and the enzyme are in close proximity to one another in the cavities of the support. The catalyst mimics a metalloenzyme and was used for dynamic kinetic resolution of a primary amine in high yield and excellent enantioselectivity.

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Highly dispersed palladium nanoparticles (1-2 nm) supported in large-pore mesocellular foam (MCF; 29 nm) were synthesized. The Pd-nanocatalyst/MCF system was characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The performance of the Pd nanocatalyst obtained was examined for amine racemization. The Pd nanocatalyst showed higher activity and selectivity toward racemization of (S)-1-phenylethyl amine than any other amine racemization catalyst reported so far and it could be reused several times. Our data from TEM and XRD suggest a restructuring of the Pd nanocatalyst from amorphous to crystalline and an increase in Pd nanocatalyst size during the racemization reaction. This led to an unexpected increase of activity after the first use. The Pd nanocatalyst obtained can be integrated with other resolving processes of racemic organic compounds to increase the yield of chiral organic products.

Metal nanoparticle growth represents a major deactivation mechanism of supported catalysts and other functional nanomaterials, particularly those based on low melting-point metals. Here we investigate the impact of the support porous structure on the stability of CuZnO/SiO2 model methanol synthesis catalysts. A series of silica materials with ordered cagelike (SBA-16 mesostructure) and disordered (SiO2-gel) porosities and varying pore sizes were employed as catalyst supports. Nitric oxide moderated nitrate decomposition enabled the synthesis of catalytically active Cu nanoparticles (3-5 nm) exclusively inside the silica pores with short interparticle spacings. Under relevant reactive conditions, confinement of the Cu particles in cagelike silica pores notably enhances catalyst stability by limiting Cu particle growth as compared to catalysts deposited in SiO2-gel host materials with also 3D and highly interconnected though unconstrained porosity. For both pore morphologies, we find a direct relationship between catalyst stability and support porosity, provided the narrowest characteristic pore dimension is employed as a porosity descriptor. For cagelike porosities this corresponds to the size of the entrances to the nanocages. Our results point to nanoparticle diffusion and coalescence as a relevant growth mechanism under reactive conditions and underscore the significance of the narrowest pore constrictions to mitigate growth and improve catalyst stability. This finding contributes to the establishment of general and quantitative structure-stability relationships which are essential for the design of catalysts and related functional nanostructures with long lifetimes under operation conditions.

Candida antarctica lipase A (CALA) immobilized in functionalized mesocellular foam in the presence of sucrose, followed by lyophilization, led to a dramatic increase in the enantioselectivity as well as an improved thermostability of the enzyme. The immobilized lipase was used for kinetic resolution (KR) and dynamic kinetic resolution (DKR) of the β‐amino ester, ethyl 3‐amino‐3‐phenylpropanoate. The temperature of optimum activity of CALA shifted from 20–30 °C to 80–90 °C on immobilization in the MCF. An “enantiomeric ratio” E (E=νA/νB; νA and νB are the rate constants for entantiomers A and B) of 69 and a conversion of 43 % in 1 h were obtained at 80 °C, whereas non‐immobilized CALA lost its activity at T≥50 °C. The obtained immobilized CALA showed an E value of greater than 500 at 22 °C. Combination of the immobilized CALA with a ruthenium complex, acting as a racemization catalyst, allowed for a successful DKR of ethyl 3‐amino‐3‐phenylpropanoate resulting in 85 % conversion and 89 % ee.