Gas foaming guided fabrication of hydrogel beads with controlled phase and porous structure for durable and highly efficient solar-powered water purification

•The novel foam HHBs controlled pore geometry via gas-assisted foaming-crosslinking method.•An evaporation rate of 3.58 kg m−2h−1 at 94.7% energy efficiency.•Effective energy utilization based on the hierarchical water transport and tailored water state.•Over 3.3 kg m−2h−1 achieved even after 96 h in a 25 wt% brine.•Marangoni effect on individual spherical surface boosted water evaporation and salts backflow.