Fig. 2. (a) X-ray crystal structure of 1a and molecular model (see text) of 1b. Biphenyl-4-phosphonate units of 1b were modeled within the outer shell, which was also determined by X-ray crystal structure analysis. The outer shells of both MOPs are in blue wire-frame representation, while the interior organophosphonates are in the space-filling model; (b) ³¹P NMR and (c) ¹H NMR spectra of base-digested samples (400 MHz, NaOD/D₂O, 293 K) of VMOC-2, 1a, and 1b.