Polymerization confined to the pore was first adapted for the nanoscale structure adjustment of adsorption resin. The self-cross-linked polymer (P-1) formed in the pore of hyper-cross-linked resin (HR) by the Friedel-Crafts reaction of p-dichloroxylene (p-DCX), occupying the macropore of the HR resin and bringing about an external micropore. Compared with the raw HR resin, the volume of the micropore of HR@P-1 in 0.4 < D < 1 nm increased but the volume of the macropore has obviously decreased. After the loading of P-1 in the nanopore of HR, HR@P-1 has better gas adsorption performance. At 298 and 100 KPa, the adsorption capacity of CO2 is almost 30% higher than that of HR, reaching 35.7 cm3/g, due to the increase in the smaller micropore volume. Moreover, HR@P-1 has also been found to be the first C2H6-selective adsorption resin. The uptake of C2H6 is up to 56 cm3/g, and the IAST selectivity of C2H6/CH4 reaches 15.3. HR@P-1 can also separate syngas efficiently at ambient temperature and be regenerated by simple vacuum operation.