Covalent Organic Framework Barriers Implanted Nanomotors Propelled by Amplified Thermal Gradients

Covalent organic frameworks (COFs) regulated by molecular engineering are successfully employed as "thermal barriers" to construct motion-enhanced photothermal nanomotors, realizing the direct experimental observation of steep asymmetric thermal gradients and precise motion regulation. The COF thermal barriers, strategically implanted between a spherical SiO₂ core and an Au hemispherical shell, effectively inhibit the isotropic diffusion of photothermal energy from the asymmetric Au shell, resulting in a 4-fold amplification of the local thermal gradient. The step thermal gradient achieved a steep 320% increase in motion speed compared to nanomotors without thermal barriers, with the remarkable highest speed up to ≈88 µm s^-1. Benefiting from the amplified thermal gradient, the asymmetric thermal field generated by COF barriers is directly observed experimentally using high-resolution photothermal microscopy. Notably, the thermal conductivity of COFs can be precisely modulated through pore engineering, enabling accurate control of nanomotor speed at the molecular level. Leveraging the robust drug-loading capacity of COF, motion-enhanced COF nanomotors exhibit exceptional tissue penetration and drug delivery performance. Overall, the COF thermal barriers combine designable drug-loading pore structure with tailored thermal conductivity properties, endowing the nanomotors with potent synergistic therapeutic effects for venous thrombosis via enhanced local photothermal ablation and heat-triggered drug delivery.