Reticular photothermal traps enabling transparent coatings with exceptional all-day icephobicity

Inhibiting ice formation is important in many applications as well as for tackling the global energy crisis and natural disasters. Most passive icephobic surfaces lose the icephobicity in extremely cold environments due to heat loss and inevitable heterogeneous nucleation. Here, we report a rational reticular-chemistry-engineered photothermal superhydrophobic coating to address this challenge. First, hydrophobic ∼ 20-nm metal−organic framework (MOF) nanoparticles are synthesized and dispersed in a self-healing polydimethyl siloxane (PDMS) to obtain a coating which achieves superhydrophobicity, low ice adhesion, and optical transparency. The transparency results from minimal light scattering due to an all-nanoscale hierarchy of roughness (nanohierarchy), i.e. a combination of nanoparticle or their cluster (∼100 nm-scale) and the sub-nm MOF pores. Next, we grow MOF on carbon nanotubes (CNTs) for a synergistic combination of thermal insulation (heat localisation) and photothermal trapping, while sub-nm MOF pores are expected to result in an interfacial nanoconfinement effect. Non-equilibrium molecular dynamics simulation and thermal conductivity measurements are used to understand the energy localisation and trapping, and ice nucleation experiments demonstrate the exceptional inhibition of ice nucleation and all-day extreme icephobicity. These MOF/CNT hybrid particles are dispersed in the self-healing PDMS to obtain sprayable coatings with excellent anti-icing and built-in mechanical damage tolerance featuring room-temperature healing capability. Strikingly, supercooled droplets on these surfaces at ∼−40 °C and ∼30 % relative humidity evaporated fully before freezing. The reticular photothermal traps may offer a promising strategy to obtain damage tolerant icephobic surfaces delaying freezing nearly to the homogeneous nucleation temperatures. • The photothermal property, wettability, and surface texture of carbon nanotubes were using MOF. • The transparency of the photothermal coatings was due to the all-nanoscale hierarchy of roughness. • MOF nanopores enable interfacial nanoconfinement, which passively inhibits heterogeneous ice nucleation. • Supercooled droplets on the photothermal surfaces fully evaporated at ∼-40 °C before freezing.