A kind of unconventional metal-organic framework (UMOF), hafnium phosphonates (HfP) with different molar fractions P/(P + Hf), were synthesized via a template-free, one-pot method by the reaction between hafnium chloride octahydrate (HfOCl2 center dot 8H(2)O) and amino tris(methylenephosphonic acid) (ATMP); the structure, sorption behaviors for actinides, acid resistance and radiolytic stability of the synthesized materials were then investigated. The results reveal that the materials were amorphous and porous, and HfP with a higher molar fraction P/(P + Hf) exhibited a higher sorption capacity for Th(IV) and U(VI). In 3 mol/L HNO3, K-d values of HfP for Th(IV) and U(VI) were 5.84 x 10(4) and 5.09 x 10(3) mL/g, respectively, indicating superiority to other MOF materials in strong acidic solution. The K-d values for tracer amounts of radioactive Pu-239 and Np-237 were 1.19 x 10(4) and 6.68 x 10(3) mL/g in 4 mol/L HNO3, respectively. This is the first case of applying MOF materials to capture transuranic elements from a strong acidic medium. Moreover, the materials were quite stable when dipped into strong acidic solutions, while their sorption performances were unexpectedly enhanced after irradiated by high dosage gamma-rays in air. All the results support its anticipated application as actinide sorbents in many practical nuclear processes.