Universal confined-ion assembly of rose-like architectures across multiple MXenes for energy storage

Assembling two-dimensional (2D) MXene nanosheets into stable three-dimensional (3D) architectures is crucial for unlocking their potential in energy storage and adsorption applications. However, the inability of directional forces to overcome strong interlayer interactions under ambient conditions fundamentally limits the formation of stable 3D MXene structures. Herein, we unveil a universal confined-ion strategy that drives the 2D-to-3D transition inside natural wood microreactors. Potassium ions neutralize the surface charge of MXene nanosheets, triggering the formation of petal-like units, and spatial confinement guides their non-planar assembly into rose-like assemblies with tunable dimensions from 1.0 to 10.2 μm. Compared with 2D MXene, the resulting 3D MXene assemblies exhibit a 16.1-fold larger specific surface area and outstanding electrochemical performance, delivering gravimetric and areal capacitances of 895.9 F g^-1 and 4.3 F cm^-2 with 100% retention after 10,000 cycles. The MXene assemblies also exhibit excellent multifunctionality, achieving 1.9 kg m^-2 h^-¹ solar evaporation rate and 99.1% dye removal efficiency. Importantly, this strategy is universal across a range of MXene, offering a scalable and versatile platform for constructing robust 3D architectures from MXene.