Abstract: Solar-driven interfacial evaporation technology provides a green and sustainable approach to alleviating water scarcity. However, conventional evaporators still suffer from insufficient pollutant removal capability and limited long-term operational stability in complex contaminated water treatment. Herein, a multifunctional phosphorylated cellulose-based photothermal composite aerogel was fabricated through a multicomponent synergistic construction strategy. In this system, phosphorylated nanocellulose (P-CNF) introduces abundant phosphate groups to improve hydrophilicity and provide active adsorption sites, carbon black (CB) endows the aerogel with excellent photothermal conversion capability, and the poly(acrylamide-co-methacrylic acid) P(AM-co-MAA) crosslinked network further enhances structural stability and facilitates water transport. Benefiting from the three-dimensional interconnected porous architecture and synergistic interactions among functional components, the composite aerogel exhibits efficient adsorption capability toward reactive yellow (RY) dye, achieving an equilibrium adsorption capacity of approximately 107.5 mg·g⁻¹ at an initial concentration of 30 mg·L⁻¹. Moreover, the adsorption process follows the pseudo-second-order kinetic model. Meanwhile, the continuous hydrophilic network promotes the transport of contaminated water to the evaporation interface, where the photothermal conversion ability of CB enables the synergistic integration of pollutant capture and solar-driven water evaporation. Under one-sun illumination (1.0 kW·m⁻²), the aerogel achieves an evaporation rate of approximately 2.21 kg·m⁻²·h⁻¹ in pure water and maintains efficient evaporation performance in salt solution and dye-contaminated water systems. After 10 consecutive evaporation cycles, the evaporation rate remains at approximately 96% of its initial value, demonstrating outstanding cycling stability. This work develops a multifunctional cellulose-based water purification material integrating pollutant adsorption, solar energy conversion, and water recovery, providing a promising strategy for the design of green, efficient, and sustainable solar-driven water purification systems.