Synergistic Interfacial Water Evaporation and Photothermal Activation in COF/MXene Aerogels for Solar CO₂ Reduction

Achieving efficient and selective solar-driven CO₂ reduction remains a grand challenge due to sluggish proton-electron transfer kinetics and limited reactant availability at catalytic interfaces. Herein, we present a hierarchically structured aerogel integrating triazine-based covalent organic frameworks (TCOF) with Nb₂CT_x MXene nanosheets embedded in a poly(vinyl alcohol)/sodium alginate (PVA/SA) matrix. The aerogel leverages broadband light harvesting, hierarchical water regulation, and localized photothermal activation to enhance multielectron CO₂ conversion. The hydrophilic-hydrophobic PVA/SA scaffold promotes rapid water uptake and vapor-phase transport, while Nb₂CT_x enables efficient near-infrared-induced heating to establish a proton-rich interfacial microenvironment. Simultaneously, the porous TCOF network offers abundant CO₂ adsorption and activation sites. This synergistic architecture facilitates stable proton-coupled electron transfer (PCET) pathways and C-C coupling. In situ spectroscopic analyses reveal enhanced formation and stabilization of *COOH, *CH₃, and *OCCHO intermediates under photothermal conditions, evidencing facilitated C-C coupling for C₂ product generation. Under 3-sun irradiation for 3 h, the optimized TCOF/Nb₂CT_x aerogel delivers exceptional yields of 119.3 μmol·g^-1 CH₄ and 94.9 μmol·g^-1 C₂H₄, which is 2-fold higher than powder analogues and surpassing previous COF/MXene systems. This work demonstrates a generalizable strategy to engineer carbohydrate polymer-based aerogels with integrated light-to-heat conversion, vapor regulation, and catalytic site accessibility for efficient solar-to-chemical fuel generation.