Encapsulation of heteropolyacids within hollow microporous polymer nanospheres for sustainable esterification reaction

Herein, the Keggin structural phosphotungstic acid (HPW) has been successfully encapsulated within hollow microporous polymer nanospheres (H-MPNs) by a “ship-in-bottle” approach. The H-MPNs are formed by self-assembly induced by hyper-crosslinking of polylactide-b-polystyrene (PLA-b-PS). The obtained catalysts (HPW@H-MPNs) exhibit more sustainable availability than the previously reported HPW-supported catalysts in esterification reaction. This excellent sustainability can be attributed to the stable microporous channels in H-MPNs which are smaller than the molecular size of HPW, thereby effectively preventing the HPW from leaking out. Moreover, such catalysts also perform well in terms of catalytic activity and universality because of the combination of a hollow structure in the interior and permeable pore channels in the shells. This type of polymer carrier and general encapsulation method may provide a new strategy for developing more sustainable catalysts for various chemical reactions.