Anion-induced differential assembly and structural transformation of supramolecular coordination cages

The intimate host-anion interactions will regulate thermodynamics and kinetics in the self-assembly of cationic cages mimicking biological counterparts. Herein, we report construction and transformation of three Pd(II)-based metal-organic cages (MOCs) depending on different anions. Stoichiometric conversions of the lantern-shaped MOC-34 into either octahedral MOC-35 or tricapped trigonal prism MOC-36 are induced by BF4‒ or NO3‒, respectively. MOC-36 is kinetically favored and can undergo quantitative conversion to the thermodynamically preferred MOC-35 upon heating, accelerated by excess BF4‒ to motivate dissociative dynamics of Pd-vertices and lower activation barrier of cage transformation. The guest encapsulation behaviors of MOC-35 and MOC-36 have also been tested. These results manifest a significance of host-anion dynamics beyond complementary anion template, shedding light on the understanding of intricate anion recognition in nature.