A Polyoxoniobate‐Based Molecular Heterojunction Orchestrates Heat and Vapor Transport for Efficient Solar Evaporation

ABSTRACT Efficient solar‐driven interfacial evaporation requires precise coordination of heat and mass transport, yet achieving such synergy within conventional molecular systems remains challenging. Here, we address this limitation using an atomically precise polyoxoniobate (PONb)‐based molecular heterojunction, [Te 5 Cu 0.2 Nb 15 O 57 H 5.6 ][(CuL) 7 (OH)]·21H 2 O (PONb‐CuL, L = 2,2′‐bipyridine), in which hydrophilic PONb clusters are covalently integrated with photothermal organocopper CuL units. This Janus molecular architecture couples broadband solar absorption with interfacial water‐cluster regulation within a single framework. Under one‐sun irradiation, a two‐dimensional PONb‐CuL evaporator delivers an evaporation rate of 2.87 kg m −2 h −1 . Incorporation into a three‐dimensional aerogel architecture further boosts the evaporation rate to 5.34 kg m −2 h −1 , affording a freshwater yield of 29.25 L m −2 under outdoor operation. Ab initio molecular dynamics simulations reveal that the PONb domain promotes hydrogen‐bonded water‐cluster formation, whereas the organocopper domain reduces the energy barrier for interfacial water transport and vapor escape. This work introduces polyoxometalate‐based molecular heterojunction engineering as a strategy for orchestrating coupled heat and mass transport, offering critical insights into the rational design of efficient solar‐to‐vapor conversion systems.