Polydopamine-coated polystyrene (PS@PDA) nanospheres which are prepared by self-polymerizing of dopamine on the surfaces of polystyrene (PS) nanospheres show excellent Cu2+ adsorption capacity. The Cu2+ adsorption capacity of PS@PDA can even reach 178 mg/g in about 6 min, which is superior to the other adsorption materials reported in literatures. Through linear fitting, it can be seen that Cu2+ is chemisorption covered by multilayers on the surface of PS@PDA, with less affect by temperature. The PS@PDA nanosphere with good adsorption capacity is first applied as the Cu2+ adsorbent and then recycled to preparation of PS nanocomposite with enhanced flame retardancy, great smoke and toxic gases suppression properties. To overcome the drawbacks of evaluation methods reported before, a new evaluation system of analytic hier-archy process is first applied to comprehensively analyze fire safety of samples. The average value of smoke production rate of PS@PDA absorbed 5 mg/L Cu2+ (PS 2) reduces by about 10%, and the average and total yield of carbon monoxide of PS 2 decrease by 15.7% and 18.1% compared with that of neat PS, respectively. PS 2 with the highest score of 86.75 has the best comprehensive fire safety performance among all samples. This work provides a guideline for green flame-retardant chemistry. (c) 2020 Elsevier Inc. All rights reserved.