This　work　demonstrates　that　the　use　of　high-negative　and　high-symmetry　lacunary　polyoxometalates　(POMs)　for　the　clustering　of　alkali　metal　ions　is　a　feasible　strategy　not　only　for　the　formation　of　rare　high-nuclearity　alkali-metal　clusters　but　also　for　the　construction　of　new-type　all-inorganic　ionic　porous　materials.　By　the　strategy,　an　unprecedented　high-nuclearity　K-H2O　cluster　{K42(H2O)60}　with　core–shell　K6@K36　configuration　is　stabilized　by　8　C3v-symmetry　trivacant　POMs　[GeW9O34]10−,　forming　a　novel　giant　ionic　alkali-metal-POM　composite　cluster　{K42Ge8W72O272(H2O)60}　with　more　than　100　metal　centers.　The　incorporated　42-nuclearity　K-H2O　cluster　{K42(H2O)60}　exhibits　the　highest-nuclearity　alkali-metal-water　cluster　known　to　date　in　POM　chemistry.　Further,　the　giant　{K42Ge8W72O272(H2O)60}　clusters　can　be　linked　by　another　kind　of　alkali　metal　ions　Na+　to　generate　a　fascinating　three-dimensional　all-inorganic　ionic　porous　framework　with　high　chemical　stability,　proton　conductivity,　and　water　vapor　adsorption.　©　2018　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim