The　type　of　inorganic-organic　hybrid　polymeric　material　formed　by　the　coordination　of　phosphonate　ligands　to　metal　ions,　resulting　in　multi-dimensional　extended　assemblies　is　metal　phosphonates　(MPs).　The　discipline　of　MPs　chemistry　has　developed　progressively　over　the　last　few　decades,　fueled　by　interest　in　applications　in　a　wide　range　of　fields.　Synthetic　technologies　of　MPs　are　lacking　on　the　way　to　domestic,　more　efficient　alternatives.　For　the　characterization,　the　advancement　of　electron　diffraction　as　an　instrument　for　crystal　structure　determination　and　the　use　of　in　situ　characterization　techniques　have　allowed　for　a　better　understanding　of　reaction　pathways.　Metal　phosphonates　have　been　discovered　to　be　appropriate　materials　for　a　wide　range　of　applications.　This　chapter　continues　to　concentrate　on　advanced　emerging　applications　of　MPs　in　bio-ceramics,　electrochemical　energy　devices,　fuel　cells,　state-of-the-art　hydrogen　evolution　rate　(HER),　oxygen　evolution　rate　(OER),　and　water　splitting　catalysts.　The　remaining　eighteen　chapters　in　the　book　demonstrate　the　vast　expansion　and　diversity　of　metal　phosphonate　chemistry　research　briefly.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Switzerland　AG.