  Even micromachines with tailored functionalities enable targeted therapeutic
applications in biological environments, their controlled motion in biological
media and drug delivery functions usually require sophisticated designs and
complex propulsion apparatuses for practical applications. Covalent organic
frameworks (COFs), new chemically versatile and nanoporous materials, offer
microscale multi-purpose solutions, which are not explored in light-driven
micromachines. We describe and compare two different types of COFs, uniformly
spherical TABP-PDA-COF sub-micron particles and texturally highly nanoporous,
irregular, micron-sized TpAzo-COF particles as light-driven microrobots. They
can be used as highly efficient visible-light-driven drug carriers in aqueous
ionic and cellular media, even in intraocular fluids. Their absorption ranging
down to red light enables phototaxis even in deeper biological media and the
organic nature of COFs enables their biocompatibility. The inherently porous
structure with ~2.5 nm structural pores, and large surface areas allow for
targeted and efficient drug loading even for insoluble drugs and peptides,
which can be released on demand. Also, indocyanine green (ICG) dye loading in
the pores enables photoacoustic imaging or optical coherence tomography and
hyperthermia in operando conditions. The real-time visualization of the
drug-loaded COF microswimmers enables new insights into the function of porous
organic micromachines, which will be useful to solve various drug delivery
problems.
