Confining Co-Based Nanocatalysts by Ultrathin Nanotubes for Efficient Transfer Hydrogenation of Biomass Derivatives.

Catalytic transfer hydrogenation (CTH) based on non-noble-metal catalysts has emerged as an environmentally friendly way for the utilization of biomass resources. However, the development of efficient and stable non-noble-metal catalysts is crucially challenging due to their inherent inactivity. Herein, a metal-organic framework (MOF)-transformed CoAl nanotube catalyst (CoAl NT160-H) with unique confinement effect was developed via a "MOF transformation and reduction" strategy, which exhibited excellent catalytic activity for the CTH reaction of levulinic acid (LA) to γ-valerolactone (GVL) with isopropanol (2-PrOH) as the H donor. Comprehensive characterizations and experimental investigations uncovered that the confined effect of the ultrathin amorphous Al2O3 nanotubes could modulate the electronic structure and enhance the Lewis acidity of Co nanoparticles (NPs), thus contributing to the adsorption and activation of LA and 2-PrOH. The synergy between the electropositive Co NPs and Lewis acid-base sites of the CoAl NT160-H catalyst facilitated the transfer of α-H in 2-PrOH to the C atom of carbonyl in LA during the CTH process via a Meerwein-Ponndorf-Verley mechanism. Moreover, the confined Co NPs embedded on am-Al2O3 nanotubes endowed the CoAl NT160-H catalyst with superior stability and the catalytic activity was nearly unchanged for at least ten cycles, far surpassing that of the Co/am-Al2O3 catalyst prepared by the traditional impregnation method.

Hybrid MOF Template-Directed Construction of Hollow-Structured In2 O3 @ZrO2 Heterostructure for Enhancing Hydrogenation of CO2 to Methanol.

Direct hydrogenation of CO2  to methanol using green hydrogen has emerged as a promising method for carbon neutrality, but qualifying catalysts represent a grand challenge. In2 O3 /ZrO2  catalyst has been extensively applied in methanol synthesis due to its superior activity; however, the electronic effect by strong oxides-support interactions between In2 O3  and ZrO2  at the In2 O3 /ZrO2  interface is poorly understood. In this work, abundant In2 O3 /ZrO2  heterointerfaces are engineered in a hollow-structured In2 O3 @ZrO2  heterostructure through a facile pyrolysis of a hybrid metal-organic framework precursor MIL-68@UiO-66. Owing to well-defined In2 O3 /ZrO2  heterointerfaces, the resultant In2 O3 @ZrO2  exhibits superior activity and stability toward CO2  hydrogenation to methanol, which can afford a high methanol selectivity of 84.6% at a conversion of 10.4% at 290 °C, and 3.0 MPa with a methanol space-time yield of up to 0.29 gMeOH  gcat -1  h-1 . Extensive characterization demonstrates that there is a strong correlation between the strong electronic In2 O3 -ZrO2  interaction and catalytic selectivity. At In2 O3 /ZrO2  heterointerfaces, the electron tends to transfer from ZrO2  to In2 O3  surface, which facilitates H2  dissociation and the hydrogenation of formate (HCOO*) and methoxy (CH3 O*) species to methanol. This study provides an insight into the In2 O3 -based catalysts and offers appealing opportunities for developing heterostructured CO2  hydrogenation catalysts with excellent activity.