Carbon-13 NMR chemical shift simulations predict orbital contributions of the metal base/π-acid interactions in MOFs. We find that π-backbonding dominates the interaction as discerned from the C chemical shielding anisotropy. While the C NMR spectrum of ethylene is almost uninfluenced by forward donation-σ11, σ22, σ33 only depend on E(σ(C=C)), E(π*(C=C)), E(σ(C-H))-the extent of forward donation can best be evaluated by considering the C NMR spectrum of acetylene. The 1 H NMR spectrum of ethylene reflects the overall physical changes upon binding with the isotropic shift, directly correlating with d(C=C) and ∡(C=C-Hcent). In the future, such observations of the electronic structure may help in the design of metal sites with enhanced backbonding interactions in porous materials for gas separation. We envision our approach to be broadly relevant to the study of catalysis and gas adsorption involving alkenes and alkynes in porous framework materials.