The pairing mechanism in infinite-layer nickelates (${\mathrm{RNiO}}_2$) remains highly debated. Conventional density functional theory (DFT) predicts a weak electron-phonon coupling (EPC) that fails to account for the observed superconducting transition temperatures ($T_c$), but such estimates are limited by the well-known inability of DFT to capture strong electronic correlations. Here, we develop a consistent theoretical framework combining DFT with the GW method to quantitatively assess the electron-phonon coupling (EPC) strength across the nickelate series (R = La, Nd, Sm), and predict a novel actinide analogue (R = Ac). Our calculations reveal that $\mathit{GW}$ self-energy effects substantially renormalizes the interstitial states and rare-earth $d$ bands, bringing them closer to the Fermi level and dramatically enhancing EPC. This enhancement follows a clear monotonic trend from La to Sm, driven by a cooperative chemical-pressure mechanism (lanthanide contraction) that simultaneously increases the electronic density of states and hardens the relevant phonon modes. This synergy is consistent with the experimentally observed rise in $T_c$ and optimizes the high $T_c$ in ${\mathrm{SmNiO}}_2$. Extending this framework, we predict ${\mathrm{AcNiO}}_2$ as a promising actinide analogue with moderate EPC, providing a critical testbed for disentangling the respective roles of the rare-earth $d$ and interstitial-$s$ orbitals. Our work suggests EPC as a sizable and systematically tunable contributor to superconductivity in nickelates and offers a quantitative bridge between theory and experiment within our $\mathit{GW}$ framework, particularly regarding the critical role of interstitial states and chemical pressure, as recently revealed by angle-resolved photoemission spectroscopy.

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• Electron-phonon coupling
• Electronic structure
• Superconductivity
• High-temperature superconductors
• First-principles calculations
• GW method