Polyamidoamine dendrimer functionalized cellulose nanocrystals for CO2 capture

In this work, the CO2 capture performance of polyamidoamine (PAMAM) dendrimer functionalized cellulose nanocrystals (CNCs) of different generations (CNC-G1 similar to G4) was evaluated under dry conditions at 25-45 degrees C by thermogravimetric analysis. Compared with bare CNCs and CNC-derivatives, including carboxylated CNCs (CNC-COOH) and aminated CNCs (CNC-NH2), the PAMAM dendrimer functionalized CNC-G1 similar to G4 showed higher CO2 capture capacity under different dry conditions, demonstrating the enhanced CO2 capture performance by the PAMAM dendrimer structure on the CNCs. The second generation of PAMAM functionalized CNCs (CNC-G2) exhibited a CO2 capture capacity of 13.31 +/- 0.38 mg/g at 25 degrees C, 9.64 +/- 0.60 mg/g at 35 degrees C, and 9.18 +/- 1.27 mg/g at 45 degrees C, respectively, prevailing among all the samples. Both pseudo-first-order and pseudo-second-order kinetic models were used to fit the adsorption kinetics, while the latter gave better fitting to experimental data. The activation energy obtained from the pseudo-second-order kinetic model was 55.67 kJ/mol for CO2 capture on CNC-G2, indicating an adsorption mechanism of dominant physisorption with slight chemisorption for CO2 capture. The FTIR spectra of CNC-G2 before and after CO2 adsorption-desorption cycle at 45 degrees C evidenced the formation of ammonium carbamate during CO2 capture, contributing to the high tolerance of CO2 desorption under the subsequent drier conditions (95 degrees C in N-2 gas flow).

Automated summary

The study found that PAMAM dendrimer functionalized CNCs had higher CO2 capture capacity compared to bare CNCs and other derivatives, with CNC-G2 showing the best performance. The pseudo-second-order kinetic model provided a better fit to the adsorption kinetics, with an activation energy of 55.67 kJ/mol indicating dominant physisorption mechanism for CO2 capture. The FTIR spectra confirmed the formation of ammonium carbamate during CO2 capture, contributing to high tolerance of CO2 desorption under subsequent drier conditions.