The development of polymer reticulated foams with high expansion ratios (VER) for selective oil-adsorption applications has been hindered by technical challenges. In this article, high VER reticulated foam with outstanding selective oil-adsorption performance was realized through the synergistic effect of molecular topological structure and blending heterostructure. Branched polybutylene terephthalate(B-PBT)/thermoplastic polyester elastomer(TPEE) was prepared by blending reaction. Then, B-PBT/TPEE blends were foamed by supercritical CO2 melting foaming, a solvent-free process. The nano-scale TPEE, acting as the weak point, induced the cell wall to rupture and form reticulated foam after the B-PBT had expanded to a high VER. The branching topological structure endowed PBT high storage modulus(G’) and complex viscosity(η*), which support the expansion of foam and keep foam from collapsing before the melt solidification. As a result, ultra-high VER three-dimensional reticulated foams possessing VER of 46.9 and open-cell content of 97.8 % were prepared, which is higher about 200 % than the previous research. The water contact angle of reticulated foams is 132° and cyclohexane droplets diffuse into reticulated foam showing the contact angle of 0°, indicating the reticulated foam have oleophilicity and hydrophobicity. The adsorption capacity of the reticulated foam for various oils is from 24 to 67 g/g. Moreover, the adsorption rate constant of reticulated foam is 8 times more than that of conventional open-cell foam. These benefits from the unique cell structure and high VER of reticulated foam. The work provides a facile and novel method for the green preparation of high-performance oil/water separation materials.