Insight into the In-Situ Encapsulation-Reassembly Strategy To Fabricate PW<sub>12</sub>@NiCo-LDH Acid–Base Bifunctional Catalysts
Huaiying Zhang, Dongyuan Cui, Tianyang Shen, Tong He, Xuejie Chen, Sai An, Bo Qi, Yu‐Fei Song
Abstract
Acid–base bifunctional catalysts have attracted increasing attention due to the improved overall efficiency of synthetic reactions. Herein, we reported the successful fabrication of a PW 12 @NiCo-LDH acid–base bifunctional catalyst by using the in-situ encapsulation-reassembly strategy. The evolution process of morphology and structure was monitored carefully by various time-dependent characterizations. X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculations demonstrated that the terminal oxygen of PW 12 in PW 12 @NiCo-LDH preferred to assemble with the oxygen vacancies on NiCo-LDH. When applied for deacetalization-Knoevenagel condensation, the PW 12 @NiCo-LDH displayed >99% conversion of benzaldehyde dimethyl acetal (BDMA) and >99% yield of ethyl α-cyanocinnamate (ECC). Moreover, PW 12 @NiCo-LDH can be recycled at least 10 cycles without obvious structural change, which can be attributed to the confinement of PW 12 into the NiCo-LDH nanocage. Such excellent catalytic activity of PW 12 @NiCo-LDH was benefited from the short mass transfer pathway between acid sites and base sites, which was caused by the stable assembly between PW 12 and NiCo-LDH.