CONG Peiao，WANG Rongyao，LI Chunsheng，CHEN Guozhu

School of Chemistry and Chemical Engineering，University of Jinan，Jinan 250022，China

Abstract

Objective To improve the conversion rate and selectivity of phenylpropionaldehyde（HCAL）in cinnamaldehyde（CAL）hydrogenation， and to verify the effectiveness of covalent organic framework （COF） as a shell to improve the performance of heterogeneous catalytic hydrogenation，a selective catalytic hydrogenation catalyst with a sandwich-like structure is prepared.

Methods A metal-organic framework （MOF）， Ce-UiO-66-NH₂ （Ce-MOF）， was synthesized as a core via solvothermal method. Using the colloidal impregnation method， platinum（ Pt） metal nanoparticles（ NPs） were uniformly loaded on the surface of the Ce-MOF core to obtain Ce-MOF@Pt. 2，4，6-trihydroxy-1，3，5-benzenetricarbaldehyde （Tp） and p-phenylenediamine （Pa） were added via solvothermal method to construct a covalent organic framework （COF） shell， TpPa-COF. The shell was then covalently bonded to the Ce-MOF through a C-N bond to prepare the composite catalyst Ce-MOF@Pt@TpPa-COF with CeMOF as the core， Pt NPs as the intermediate layer， and TpPa-COF as the shell. Thecatalyst TpPa-COF@Pt was also prepared， and the the structures and performance of Ce-MOF@Pt， Ce-MOF@Pt@TpPa-COF， and TpPa-COF@Pt were compared regard⁃ ing to the conversion rate， selectivity， and stability of the three catalyst groups during the hydrogenation of CAL to HCAL.

Results and Discussion At a reaction time of 6 h， the conversion rates of CAL for Ce-MOF@Pt， Ce-MOF@Pt@TpPa-COF， and TpPa-COF@Pt were 92%， 89%， and 99%， respectively. The selectivities for the target product HCAL were 21%， 50%， and 1%， respectively. The yields of the target product HCAL were 19%， 45%， and 1%， respectively. Compared to Ce-MOF@ Pt and TpPa-COF@Pt， Ce-MOF@Pt@TpPa-COF effectively maintained activity and stability at high temperatures and exhibited stronger resistance to deactivation.

Conclusion In the catalytic hydrogenation of CAL， Ce-MOF@Pt@TpPa-COF significantly improves the selectivity and yield of HCAL in heterogeneous catalytic hydrogenation reactions while maintaining better cyclic stability. The study provides insights into the research and applications of sandwich-like structure catalysts with TpPa-COF as the shell in heterogeneous catalysis.

Keywords： sandwich-like structure； metal-organic framework； covalent organic framework； cinnamaldehyde； selective hydrogenation