MOF‐Derived Cu‐TiO 2 /Alginate Micromotors for Buoyancy‐Regulated 3D Motion

ABSTRACT Micro‐ and nanomotors (MNMs) promise impact in the areas of environmental remediation and biomedicine, but reliable three‐dimensional (3D) control remains challenging. Conventional bubble‐propelled MNMs can move in 3D, yet their trajectories are stochastic and energy‐inefficient. Here we introduce a buoyancy‐regulated strategy inspired by cyanobacteria‐like microvesicles. We engineer sodium‐alginate (SA)hydrogel magnetic micromotors (SA/Cu‐TiO 2 /Fe 3 O 4 ), in which Cu‐TiO 2 is derived from the Ti‐based metal–organic framework MIL‐125(Ti v ), yielding a porous and defect‐rich photocatalyst with uniformly distributed Cu sites for enhanced H 2 O 2 decomposition and photocatalytic activity compared with pristine TiO 2 . Upon illumination, Cu‐TiO 2 catalyzes H 2 O 2 decomposition to generate O 2 pockets that are retained within the elastic, semipermeable alginate matrix, enabling programmable flotation and precise control of vertical ( Z ‐axis) position as part of full 3D navigation. We analyze the energetics and cross‐scale mass‐transport mechanisms governing this buoyancy control, and we demonstrate guided 3D motion through a maze via magnetic steering. In model turbid water, the micromotors achieve high removal performance across diverse organic contaminants. This bioinspired platform provides a prototype and motion‐control paradigm for 3D‐motile MNMs, advancing practical remediation in aquatic environments.