In recent years, the isolated single-atom site (ISAS) catalysts have attracted much attention as they are cost-effective, can achieve 100% atom-utilization efficiency, and often display superior catalytic performance. Here, we developed a biomass-assisted pyrolysis-etching-activation (PEA) strategy to construct ISAS metal decorated on N and B co-doped porous carbon (ISAS M/NBPC, M = Co, Fe, or Ni) catalysts. This PEA strategy can be applied in the universal and large-scale preparation of ISAS catalysts. Interestingly, the ISAS M/NBPC (M = Co, Fe, or Ni) catalysts show multi-functional features and excellent catalytic activities. They can be used to conduct different types of catalytic reactions, such as O-silylation (OSI), oxidative dehydrogenation (ODH), and transfer hydrogenation (THG). In addition, we used the transfer hydrogenation of nitrobenzene as a typical reaction and revealed the difference between ISAS Co/NBPC and ISAS Co/NPC (N-doped porous carbon) catalysts by density functional theory (DFT) calculations, and which showed that the decreased barrier of the rate-determining step and the low-lying potential energy diagram indicate that the catalytic activity is higher when ISAS Co/NBPC is used than that when ISAS Co/NPC is used. These results demonstrate that the catalytic performance can be effectively improved by adjusting the coordination environment around the ISAS.