All the DFT calculations on a subset of MFI models were carried out in the CASTEP software package and employed the PBE exchange-correlation functional with the plane-wave energy cutoff of 700 eV and a k-point sampling grid of 1 × 1 × 1, ensuring that the total energy was converged to within 10 -8 eV per atom. The NMR tensors were computed using the GIPAW (gauge-including projector augmented-wave) method.