Fundamental understanding of gas physisorption is essential for energy storage, transport and utilization. Natural gas (mainly methane) is an attractive energy resources due to its high energy density and low carbon intensity. A detailed understanding of methane/surface interactions is important for improving methane storage in porous materials. Here, we are developing quantum-level descriptions of these interactions in models of porous carbon systems. Using high-level quantum theories (CCSD(T)/def2-QZVPPD with DLPNO and/or F12 approximations) as benchmarks, we evaluated 90+ DFT functionals on representative examples for methane and porous carbon adsorption models. Five accurately performing DFT functionals were selected to describe a network of C–H...\(\pi\) H-bonding and \(\pi\)...\(\sigma^{\ast}\) (C–H), and C–H...\(\sigma^{\ast}\) (C–H) tetrel interactions at reasonable computational costs. Computational maquettes were established in order to capture methane adsorption structures and energetics on open carbon surfaces (>15 Å), in between small (~7 Å) and large (~11 Å) pores. The experimental isosteric heat of adsorption can be estimated from the linear combinations of methane binding energies in various pore sizes. This work provides useful guidance for the experimental design of adsorbent materials. The modeling strategy is being extended to other gases, including \(H_2\), \(CO_2\), and \(NH_3\), as well as to more realistic adsorbent surface models with curvature, surface defect, and presence of heteroatoms.