Fully Floatable Mortise‐and‐Tenon Architecture for Synergistically Photo/Sono‐Driven Evaporation Desalination and Plastic‐Enabled Value‐Added Co‐Conversion of H2O and CO2

Abstract Establishing an advanced ecosystem incorporating freshwater harvesting, plastic utilization, and clean fuel acquisition is profoundly significant. However, low‐efficiency evaporation, single energy utilization, and catalyst leakage severely hinder sustainable development. Herein, a nanofiber‐based mortise‐and‐tenon structural Janus aerogel (MTSJA) is strategically designed in the first attempt and supports Z‐scheme catalysts. By harnessing of the upper hydrophilic layer with hydrophilic channels embedding into the hydrophobic bottom layer to achieve tailoring bottom wettability states. MTSJA is capable of a fully‐floating function for lower heat loss, water supply, and high‐efficiency solar‐to‐vapor conversion. Benefiting from the ultrasonic cavitation effect and high sensitivity of materials to mechanical forces, this is also the first demonstration of synergistic solar and ultrasound fields to power simultaneous evaporation desalination and waste plastics as reusable substrates generating fuel energy. The system enables persistent desalination with an exceptional evaporation rate of 3.1 kg m −2 h −1 and 82.3% efficiency (21 wt.% NaCl solution and 1 sun), and realizes H 2 , CO, and CH 4 yields with 16.1, 9.5, and 3 µmol h −1 g −1 , respectively. This strategy holds great potential for desalination and plastics value‐added transformation toward clean energy and carbon neutrality.