Semihydrogenation　of　acetylene　in　the　ethylene　feed　is　a　vital　step　for　the　industrial　production　of　polyethylene.　Despite　their　favorable　reaction　activity　and　ethylene　selectivity,　the　Pd-based　intermetallic　compound　and　single-atom　alloy　catalysts　still　suffer　from　the　limitation　of　atomic　utilization　derived　from　the　partial　exposure　of　active　Pd　atoms.　Herein,　a　hard-template　Lewis　acid　doping　strategy　is　reported　that　can　overcome　the　inefficient　utilization　of　Pd　atoms.　In　this　strategy,　N-coordinated　isolated　single-atomic　Pd　sites　are　fully　embedded　on　the　inner　walls　of　mesoporous　nitrogen-doped　carbon　foam　nanospheres　(ISA-Pd/MPNC).　This　synthetic　strategy　has　been　proved　to　be　applicable　to　prepare　other　ISA-M/MPNC　(M　=　Pt　and　Cu)　materials.　This　ISA-Pd/MPNC　catalyst　with　both　high　specific　surface　area　(633.8　m(2)　g(-1))　and　remarkably　thin　pore　wall　(1-2　nm)　exhibits　higher　activity　than　that　of　its　nonmesoporous　counterpart　(ISA-Pd/non-MPNC)　catalyst　by　a　factor　of　4.　This　work　presents　an　efficient　way　to　tailor　and　optimize　the　catalytic　activity　and　selectivity　by　atomic-scale　design　and　structural　control.