We　report　the　implementation　of　the　ligand-to-metal　charge　transfer　(LMCT)　in　organic　semiconductors　for　improved　full　visible-light　photocatalysis　and　understanding　of　the　effects　of　Pd-N　weak　coordination　of　a　single-atomic　Pd(II)　embedded　2D　g-C3N4　(Pd-1/UTCN)　homogeneous　catalyst　analogues　on　the　formation　of　open　metal　sites　and　LMCT　induced　full-visible-light　photocatalytic　performance.　LMCT　between　Pd(II)　and　g-C3N4　allows　for　wide-range　visible　light　harvesting　and　promoting　the　transport　of　photogenerated　charge　of　carbon　nitride　from　excitation　site　to　active　site.　Compared　to　the　porphyrin　palladium　complex　with　strong　Pd-N　coordination,　the　reversible　coordination　dissociation　of　Pd-N　of　Pd-1/UTCN　allows　for　the　formation　of　open　active　sites　photocatalysis,　which　enables　the　efficient　adsorption,　activation,　and　conversion　of　substrates.　The　adsorption　of　the　substrate　can　promote　LMCT　between　Pd(II)　and　heptanazine　ligands.　As　a　result,　Pd-1/UTCN　exhibited　LMCT-induced　efficient　full-visible-light　photocatalytic　activity　of　Suzuki　reaction　with　high　selectivity　without　additional　phosphorus　ligands.