Aiming to develop a novel series of high‐performance and organo‐soluble polyamides (PAs), two imidazole‐based diamines containing xanthene and voluminous pendant units were designed and polycondensed with common dicarboxylic acids. The polymers' excellent solubility in many organic solvents can be correlated to the introduction of flexible ether linkages and bulky pendant groups into the rigid structure of PAs. PAs possessed high thermal resistance (T10>420°C), high glass transition temperatures (Tg) (from 181 to 262°C), and inherent viscosities at 0.45–0.69 dl/g. Also, all PAs indicated good antimicrobial activity and photophysical properties due to the existence of imidazole and xanthene units in their main backbone. Furthermore, in the present research, one of the PAs (i.e., PA‐bII) was grafted onto the surface of modified‐SiO2 nanoparticles, and polymeric nanocomposite (PANC) was prepared. Obtained data from the investigation of properties of prepared PANC proves the increment in the heat resistance, antimicrobial inhibition, and photoluminescence intensity compared to neat PA. In the following, the application of PAs and PANC as absorbents to eliminate two heavy metal ions Hg2+ and Co2+ from aqueous solutions was investigated.