In this study, we developed a sustainable nanocatalyst, AXFe, by functionalizing magnetite nanoparticles with an alginate-xanthine conjugate (AX). This hybrid material combines magnetite's adsorption and photocatalytic properties with the CO2 fixation capabilities of alginate and xanthine. AXFe exhibited exceptional performance in the photocatalytic mineralization of toluene under simulated solar irradiation, achieving a 61.5 % conversion to CO2. Furthermore, the catalyst facilitated efficient CO2 fixation into cyclic carbonates, achieving high yields under mild conditions (70 °C, 1 atm CO2). CO2 adsorption studies revealed enhanced capture efficiency due to the synergistic interaction between AX and magnetite. The material also demonstrated excellent reusability, enabling magnetic recovery and maintaining over 90 % catalytic activity for four cycles. This straightforward synthesis from natural substrates and …