The　synthesis　of　multimodal　hierarchically　porous　materials　is　of　great　challenge　by　facile　approach.　Herein,　we　assemble　BPO4　hollow　spheres　into　macroscopic　foam　materials　with　multimodal　hierarchically　porous　structure　by　combining　down-to-up　process　and　Ostwald　ripening　effect.　Tailored　monolithic　B2O3@BPO4　foams　were　obtained　from　a　sticky　hydrogel　precursor　by　a　one-step　annealing　process.　The　foam　has　the　self-supporting　frame　of　BPO4　hollow　spheres　with　covering　B2O3　nanowires　and　shows　excellent　permeability　and　relatively　high　surface　area　due　to　hierarchical　structure.　The　formation　mechanism　of　monolithic　B2O3@BPO4　foams　mainly　undergoes　inflation,　particle　aggregation,　and　Ostwald　ripening　process.　Monolithic　foams　exhibit　superior　catalytic　activity　in　oxidation　dehydrogenation　of　alkanes　due　to　the　sufficient　exposure　of　active　sites　over　the　special　frame　structure.　Furthermore,　various　monolithic　functionalized　BPO4　foam　composites　can　be　easily　synthesized　and　exhibit　superior　performance　in　different　applications　including　the　oxidation　of　carbon　monoxide,　and　the　self-driven　removal　of　organic　pollutants.　More　interestingly,　we　also　found　the　sticky　hydrogel　precursor　possesses　good　heat　shielding　effect.　This　work　provides　a　new　insight　for　constructing　multimodal　hierarchically　porous　materials　with　the　remaining　superior　property　of　nanoscale　to　cope　with　various　challenges.　[Figure　not　available:　see　fulltext.]　©　2022,　Tsinghua　University　Press.