Deformable metal-organic nanosheets@SiO₂ core-shell for heterogeneous tandem catalytic transformations

Overcoming mass transport limitations imposed by stagnant boundary layers is critical for advancing heterogeneous catalysis. Building upon strategies utilizing deformable metal-organic nanosheets (MONs) to enhance diffusion, we report the synthesis of well-defined core-shell microspheres that integrate flexible and functional two-dimensional MONs. Nonporous carboxyl-terminated SiO₂ nanoparticle cores are seamlessly enveloped by ultrathin Zr-MON shells through a facile bottom-up approach. The resulting MON@SiO2 architecture exposes abundant coordinatively unsaturated Zr(IV) Lewis acid sites on its deformable nanosheets. Further introduction of the triethylenediamine (DABCO) moieties into the MON produces MON-DABCO@SiO2, enabling the co-existence of isolated Lewis acid and base sites amenable to promoting challenging reactions that are unachievable by homogeneous systems. These dynamic core-shell structures significantly enhance molecular diffusion to the active sites, as evidenced by ultra-efficient catalysis (>99% yield) in the one-pot hydrolysis-Knoevenagel tandem reactions across broad-scope substrates. Importantly, the SiO₂ core confers exceptional structural durability, enabling great catalytic recyclability for at least 5 consecutive cycles without any degradation of the performances, which is in stark contrast to the unsupported MONs. This work therefore establishes core-shell engineering of deformable MONs as a versatile approach for architecting high-performance and durable heterogeneous catalysts by synergistically combining enhanced mass transport with nanoconfinement effects.