Porous ceramic materials are currently used as volumetric sunlight absorbers in concentrating solar power systems. As the efficiency of thermodynamic cycles rapidly increases with the operating temperature, the favorable characteristics of so-called ultra-high temperature ceramics (UHTCs) can be successfully exploited in novel solar absorbers. The present work reports, for the first time to the best of our knowledge, on optical properties and microstructural analysis of novel ice-templating porous ZrB2 UHTCs, to evaluate their potential as volumetric solar receivers. We demonstrate that the different complex structures that can be obtained with the freeze casting technique show promising optical properties. The idea of conjugating an highly tailorable morphology, useful for optimizing gas fluxes and heat exchanges between absorber and gas, to the spectral selectivity which is a characteristics of ZrB2 can be a promising route for increasing the efficiency of thermal solar systems. (C) 2015 Elsevier B.V. All rights reserved.