According to the Intergovernmental Panel on Climate Change, CO2 capture using liquid absorbents is a key strategy for mitigating climate change. However, the energy footprint of the technique is still high and novel solutions are needed to design better units. To that end, this study presents a novel and detailed diffuse-interface model for interfacial mass and heat transfer coupled with chemical reactions for CO2 capture. Two scalar transport equations describe the species evolution in each phase, coupled through a variable apparent Henry’s constant that captures non-ideal vapor–liquid equilibrium at the interface. Momentum and energy transport are modeled through single-scalar formulations, with interfacial velocity discontinuities arising from reactive phase change, handled via a Stefan condition. A conservative phase-field method closes the equations, with regularization applied to suppress numerical diffusion when tracking the interface. The model resolves key physical phenomena, including reaction kinetics, mass transfer resistance, H2O phase change, and interfacial velocity jumps during both absorption and desorption. A sensitivity analysis shows that increasing the solvent mole fraction enhances chemical reactivity but increases diffusive resistance, inducing complex nonlinear effects on the interfacial reactive transport. The coupled CO2 and H2O interphase transport are captured simultaneously, with water evaporation shown to have limited impact on CO2 uptake and on the interfacial reactive Stefan velocity for isolated droplets. Additionally, multi-droplet simulations demonstrate that the droplet number and an imposed gas-phase mean flow significantly affect absorption rates and spatial asymmetry through droplet-droplet interactions and convective transport. The findings offer critical insights into interfacial CO2 transport in reactive, two-phase systems and supports the need for advanced numerical studies like the present one, given the lack of droplet-scale data and the limited applicability of bulk-scale experiments to localized transient interfacial processes.