Construct A Stable Co@CoxN@C Nanocomposites Upon A Dual-Ligand-MOF Manipulating Strategy:Highly-Dispersed And Composition-Adjustable CoxN Selective Hydrogenation Of Citral

The system and method to feasibly acquire metal nitrides as well as other metal interstitial compounds with adjustable surface properties has long been aspired for advanced applications.Therefore,in this paper,the following studies are conducted:(1)A dual-ligand metal-organic frameworks(MOF)was calcined at different temperatures.The compound was prepared through an N donor ligand and an N-absent ligand coordinated with Co center.From this method a series of catalysts that selected hydrogenation of citral were synthesized.Comprehensive characterizations exhibited that the catalysts were structured as Co nanoparticles(size in ca.10.0-20.0 nm)with surface composited Co_xN component in carbon coverage(denoted as Co@Co_xN@C);the illuminated advantages of Co@Co_xN@C catalysts such as high Cox N dispersion,adjustable surface distribution of Co and Cox N and active component protected by carbon.(2)The synthesized catalyst was applied to the citral hydrogenation reaction,where the selectivity to the valuable hydrogenation product is 93-98%,and the catalyst had good catalytic performance.The catalyst with the largest composition of(Co⁰+Cox N)/Co can achieve a yield of 60%(close to the highest level of reported non-precious metal catalysts)for the most valuable C=O hydrogenation product(Neroli and geraniol)with a TOF value of 0.56 s^-1.(3)The kinetic investigations further disclosed that the Ea pertinent to C=O hydrogenation could be lowered to 75.7 k J/mol on Co@Cox N@C in comparison with223.8 k J/mol on Co_xN-absent catalyst,which could be the intrinsic impetus to speed and tune reaction network toward favorable reaction direction on Co@Co_xN@C catalyst.FT-IR spectra demonstrate that Cox N as the mainly active site and facilitates the activation adsorption of polarized C=O group in citral,which will lead a highly seletivity to NOL+GOL.These findings not only present the importance and the origin to introduce and manipulate Co_xN composition on Co matrix for improving selective catalytic hydrogenation performance of?,?-unsaturated carbonyl compounds,but also provided a feasible dual-ligand-MOF modulating strategy to construct efficient metal interstitial compounds with adjustable surface structure and properties as well as metal nitride involved materials present here.