Phenanthrene, a prime polycyclic aromatic hydrocarbon (PAH) pollutant, is utilized to develop a nanoporous hypercrosslinked polymeric adsorbent (poly-PHEN-C) through the microwave-assisted process from catalyst anhydrous AlCl 3 and solvent CHCl 3 . Nanoporous poly-PHEN-C proves to be a highly effective adsorbent for adsorbing CO 2 from flue gas and removing organic dyes from wastewater. CO 2 capture capacity of 3.2 mmol g −1 at 298 K and 1 bar is ascribed to the combined effect of surface area (1472 m 2 g −1 ), micropores (1.1, 1.7 nm), pore volume (0.73 cm 3 g −1 ), and π electrons. The separation selectivity of the gas mixture, i.e., CO 2 /N 2 (15:85), is estimated from the ideal adsorbed solution theory model. Moreover, poly-PHEN-C is employed for removal of cationic (crystal violet, CV) and anionic (alizarin red S, ARS) dyes from aqueous solutions. In the batch process, it exhibits adsorption capacities of 161 mg g −1 for CV and 120 mg g −1 for ARS. In the continuous fixed-bed column process, breakthrough capacity of 300 mg g −1 is achieved for CV. Thus, the present study offers an eco-friendly approach for effectively managing three categories of hazardous pollutants, namely, PAHs, greenhouse gas CO 2 , and organic dyes, a sustainable strategy for environmental management.