Water　pollution,　which　continuously　threatens　human　health　and　the　sustainable　development　of　society,　has　become　a　major　concern.　Photocatalytic　degradation　is　an　effective　strategy　to　remove　organic　dyes　from　wastewater.　For　this　strategy,　it　is　crucial　to　select　the　appropriate　catalyst.　Using　triphenylphosphine　oxide　(OPPh3)　as　the　ligand,　phosphomolybdic　acid　as　the　anion　template,　three　new　lanthanide　complexes　[Ln　(OPPh3)(4)(H2O)(3)](PMo12O40)center　dot　4C(2)H(5)OH　(1-3)　(Ln　=　Sm,　Gd,　Tb)　were　synthesized.　The　raw　materials　for　the　reaction　are　cheap　and　readily　available.　The　convenient　synthesis　method　is　environmentally　friendly,　with　high　yield　(70%-80%).　Complexes　1-3　are　all　seven-coordinated　mononuclear　structures　centered　on　lanthanide　ions,　[PMo12O40](3-)　anions　and　solvent　molecules　are　not　coordinated　with　metal　ions.　These　mononuclear　structures　eventually　form　complicated　3D　supramolecular　structures　through　hydrogen　bonds,　Mo-O-center　dot　center　dot　center　dot　pi　or　C-H-center　dot　center　dot　center　dot　pi　weak　interactions.　Complexes　1-3　photocatalytic　degradation　of　MB　have　high　removal　rates,　as　catalysts　have　enough　stability　to　be　reused,　and　can　be　used　as　excellent　catalysts　for　the　degradation　of　dye　molecules　in　sewage.　Among　them,　the　removal　rate　of　MB　by　photodegradation　of　complex　2　was　highest　(99.50%).　In　addition,　the　effects　of　different　initial　concentrations　of　MB　solution　and　different　types　of　organic　dyes　on　the　photocatalysis　experiment　were　investigated.　The　photocatalytic　reaction　mechanism　of　complexes　1-3　was　also　studied.　Due　to　the　similar　structures　of　complexes　1-3,　they　have　almost　the　same　THz　absorption　spectra　with　different　absorption　intensity,　which　may　be　attributed　to　the　difference　of　the　number　of　weak　interactions.　Therefore,　terahertz　spectroscopy　can　be　used　as　a　sensitive　method　to　distinguish　and　determine　small　differences　between　lanthanide-organic　complexes.　This　is　the　first　time　that　this　spectrum　has　been　used　to　characterize　lanthanide　phosphine　oxide　complexes　modified　by　[PMo12O40](3-).