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Coal has a heterogenous porosity that influences its specific surface area (SSA) and CH₄ adsorption and desorption. However, the pore size distribution obtained with N₂ adsorption is only reliable at pore sizes >2 nm omitting the important contribution of micropore (<2 nm). Here, 13 coal samples from three series were measured by both the N₂ at 77 K and CO₂ at 273 K, respectively, to compared the adsorption pore structure characteristics of different coal ranks, seams, and macrolithotypes, which further revealed the influences of mesopore (2–50 nm) and micropore on CH₄ adsorption capacity at different pore sizes. The larger micropore total pore volume (TPV) contributes to the larger micropore SSA. As micropores are common and contribute extensively to most of the SSA (>99%) in these coals, a much better relationship exists between the Dubinin-Radushkevich (DR) SSA and CH₄ adsorption capacity …