By　means　of　first-principles　calculations,　the　interaction　of　twelve　different　transition　metal　atoms　(M　=　Fe,　Co,　Ni,　Cu,　Ru,　Rh,　Pd,　Ag,　Os,　Ir,　Pt,　and　Au)　of　groups　VIII-XI　with　phosphomolybdic　acid　(H3PMo12O40,　PMA),　a　newly　emerging　medium　for　trapping　transition　metal　atoms,　has　been　systematically　investigated.　The　M-PMA　systems　have　very　high　stability　with　the　binding　energies　of　transition　metals　higher　than　those　on　widely　used　metal　oxide　supports.　The　high　diffusion　barriers　of　these　single　metal　atoms　on　the　PMA　surfaces　suggest　that　they　are　sufficiently　stable　to　prevent　agglomeration.　Based　on　the　electronic　structure　analysis,　the　remarkable　stability　of　single　atoms　is　attributed　to　the　strong　mixing　between　the　d　orbitals　of　the　metal　atom　and　2p　orbitals　of　PMA　oxygens,　which　results　in　electron　transfer　from　the　metal　atoms　to　PMA,　producing　positively　charged　single　metal　atoms　which　can　be　used　for　catalytic　applications.　Finally,　we　test　the　activity　of　Pt-PMA　as　a　low-cost,　stable,　and　efficient　catalysts　for　CO　oxidation.　This　work　is　expected　to　provide　useful　insight　to　the　development　of　new　highly　efficient　heterogeneous　single　atom　catalysts　(SACs).　©　The　Royal　Society　of　Chemistry　2017.