Fig. 2: Crystal structure of NCU-1.

a The coordination environment of Zn2+. b The 2D extended framework of NCU-1. c The simplified topological structure of 2-fold interpenetration (different colors represent different single sets of the interpenetration). d The two fold-interpenetrated structure of NCU-1 produces numerous square small pockets. (Zn, magenta; C, dark gray; N, blue; O, red).