Core–Shell Heterostructured Composite Architected from a Multilanthanide-Included Phospho(III)tungstate and MIL-(53)Fe as a Nanozyme for Catalytic Oxidation of 3,3′,5,5′-Tetramethylbenzidine

The development of novel multicomponent nanozymes with high catalytic efficiency and selectivity continues to be a focal point in contemporary research. In this work, a multilanthanide-containing phospho(III)tungstate [H 2 N(CH 3 ) 2 ] 8 Na 12 H 16 [La 4 (H 2 O) 15 W 8 (tart) 3 (H 2 tart)O 20 ] 2 [H 2 P 2 W 14 O 52 ] 4 ·52H 2 O ( 1, H 4 tart = tartaric acid) was synthesized. Its polyoxoanion consists of two identical tartrate-stabilized tetra-La 3+ -substituted {La 4 (H 2 O) 15 W 8 (tart) 3 (H 2 tart)O 20 } units bridged by four multivacant Dawson-like [H 2 P 2 W 14 O 52 ] 12– fragments. Subsequently, 1 was subjected to ultrasonic treatment to form a nanofilm, which was then used as a guest material to coat MIL-(53)Fe (MILFe), preparing a series of core–shell heterostructured MILFe@ 1 composites. These MILFe@ 1 composites facilitate multielectron transfer and function as highly active nanozymes, significantly enhancing the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). Under optimized conditions, the MILFe@ 1 –2 ( 1: MILFe = 1:2) composite demonstrates robust catalytic performance over a broad TMB concentration range without the need for H 2 O 2 . This work highlights the potential of integrating lanthanide-containing polyoxometalates with metal–organic frameworks to construct core–shell heterostructured nanozymes with enhanced catalytic efficiency. Concurrently, the polyoxometalate shell enables rapid electron transfer kinetics, which is crucial for enhancing the overall catalytic performance of the system.