Construction And Mechanism Study Of Hf-sulfonic Acid Bifunctional Nanohybrids For Stereoselective Synthesis Of Renewable Trans-anethol

The increasingly severe energy crisis and environmental issues are forcing the transition from traditional fossil energy to renewable energy.Wherein,the utilization of novel green biomass resources to transform them into highly value-added platform molecules has aroused widespread attention around the world.Anethole（AN）is widely used in food additives,daily necessities and pharmaceuticals,and is widely recognized as an important high-value chemical molecule.It is usually extracted from low-efficiency natural plant essential oils and can also be obtained by organic synthesis of inorganic acids or precious metals.Therefore,with the goal of reducing dependence on natural aniseed oil supplies,a green and sustainable route using biomass substrate cascade catalysis has been developed for stereoselective production of trans-AN.In this paper,porous and recyclable non-precious metal Hf-based catalysts were prepared by solvothermal method without template.It is used to efficiently catalyze the synthesis of high-value AN from biomass-based ketone（4-MOPP）with 2-pentanol as hydrogen source and solvent through a cascade reaction of transfer hydrogenation and dehydration.The catalytic system does not need to add extra acid or base,and overcomes the harsh requirements of catalyst and reaction conditions for transfer hydrogenation.The system shows the advantages of environmentally friendly,economic and high efficiency.The research contents are as follows.（1）The porous structure and the enhanced hydrophobicity of the spherical catalyst PAS-Hf ensured the formation of more accessible and stable Lewis acid(Hf⁴⁺)and Br?nsted acid（SO₃H）active sites,which could be used for rapid conversion of biomass-based 4-MOPP to AN（100%conversion,97.2%yield）in 0.5-2 h(TOF:9.3 h^-1).Density functional theory（DFT）calculations elucidated that the addition of PAS-Hf could remarkably facilitate the conversion via decreasing the reaction energy barrier from151.33 k J mol^-1 to 48.27 k J mol^-1 of the rate-determining step.The good thermal stability and heterogeneity of the bifunctional catalyst were responsible for its constant activity for five cycles.The synergistic catalysis could be extended to more than ten kinds of aldehydes and ketones.This acid-base multi-catalytic protocol shows excellent potential in cascade biomass conversion via heterogeneous catalysis without any base or acid additive.（2）The template-free self-assembly of Hf⁴⁺and phenylphosphonic acid（PHA）was carried out by solvothermal method,and Br?nsted acid sites were introduced by simple green grinding sulfonation with p-toluenesulfonic acid（Ts OH）.Importantly,by adjusting the composite components,PA-Hf-SO₃H（1.5:1）exhibited a favorable amorphous inorganic-organic structure with high specific surface area（135.59 m²/g）,relatively large pore diameter（4.01 nm）,indispensable Lewis amd Br?nsted acid sites,and strong hydrophobicity and stability.The optimal reaction conditions were investigated by single-factor method and Response Surface Methodology（RSM）,and a high yield of 98.3%with excellent reusability was reported.Moreover,the activation energy（Ea）of the reaction was determined by kinetic study,and the possible reaction mechanism was also proposed.Last but not least,this catalytic strategy showed a wide range of substrate versatility,providing a promising catalytic strategy for the effective synthesis of AN or other high-value chemical molecules from biomass resources.