Surface Engineering of Hollow Microreactors with Catalytic Nanobrushes for Orthogonal Tandem Catalysis

Micro/nanoreactors with hollow structures have traditionally focused on the design of the internal catalytic microenvironment, while precise engineering of their external surfaces at a nanoscale level is particularly rare. Here, we develop a unique approach to elaborately engineer the surface of zeolitic imidazolate frameworks (ZIF-8)-based hollow microreactor with fluff-like nanostructures that serve as an external catalytic platform. This involves the anchoring of high-density micellar brushes onto the epidermis of ZIF-8 via surface-initiated living crystallization-driven self-assembly, followed by the rapid capture of multiple species to fabricate the catalytic nanobrushes. Such a nanoscale fluff-like surface in combination with an internal cavity that encapsulates other functional components enables specific spatial isolation of various catalysts. The resultant microreactor with external PW₁₂ nanobrushes for esterification and internal Pt─Ni alloys for hydrogenation reveals prominent activity toward a tandem conversion of p-nitrobenzoic acid into benzocaine with a high selectivity of 95.4%. Remarkably, the microreactor decorated with PW₁₂ nanobrushes can greatly prompt the catalytic efficiency of esterification with the inhibited competition from the hydrogenation reaction. Overall, this work provides an innovative guidance for the rational creation of multifunctional microreactors with fine surface nanostructures.