Designing efficient catalysts for the chemical fixation of CO₂ on reactive organics under mild conditions is very challenging from the perspectives of green and sustainable chemistry. Here we report a triazinetriamine-based porous organic polymer (TzTa-POP) and immobilized silver nanoparticles at its surface to fabricate a metal nanoparticle embedded catalyst AgNPs@TzTa-POP. The characterizations of AgNPs@TzTa-POP have been carried out by using FTIR, PXRD, TGA, SEM, EDAX, TEM, N₂ sorption and XPS analyses. The catalytic activity of Ag-NPs@TzTa-POP was evaluated in the carboxylative cyclization (intramolecular nucleophilic) of propargyl alcohols by using CO₂ as a reactant to obtain α-alkylidene cyclic carbonates. The desired α-alkylidene cyclic carbonates with high selectivity (>99%) and significantly high yield (87–98%) were achieved via atmospheric fixation of CO₂ at room temperature under easily operative reaction conditions. Furthermore, Ag-NPs@TzTa-POP showed excellent catalytic activity in the three component coupling reaction involving CO₂, aromatic/aliphatic amine and aliphatic/aromatic halide for the synthesis of value added organic carbamates. High isolated yield (∼87–95%) of the desired carabamate product was obtained using 1 atm CO₂ pressure under mild reaction conditions at room temperature. The catalyst sustains its activity for five consecutive reaction cycles for both the reactions. Post catalytic characterizations of AgNPs@TzTa-POP after five reaction cycles were carried out to figure out any materialistic changes in the metal nanoparticle embedded porous organic polymer.