Abstract: Squential infiltration synthesis (SIS), which involves diffusion-controlled penetration and subsequent chemisorption of inorganic precursor molecules inside polar domains of the block-copolymer template, is proposed as an efficient chemophysical approach to designing highly porous all-inorganic single- and multicomponent structures. We show that show that this approach can be used efficiently for fabrication of films with a low refractive index that enable design of single-layer and broadband graded-index antireflective coatings (ARCs). The refractive index can be fine-tuned via control over the characteristics of the block-copolymer templates and the number of infiltration cycles. We show that modification of the block-copolymer temperate with cations of different elements prior to the gas-phase infiltration cycles allows fabrication of multicomponent structures consisting of nanoparticles randomly distributed in the highly porous host matrix. As a result, we are able to synthetize all inorganic highly porous heterostructures with highly accessible thermally stable functional centers