Controllable　synthesis　of　ultrasmall　atomically　ordered　intermetallic　nanoparticles　is　a　challenging　task,　owing　to　the　high　temperature　commonly　required　for　the　formation　of　intermetallic　phases.　Here,　a　metal-organic　framework　(MOF)-confined　co-reduction　strategy　is　developed　for　the　preparation　of　sub-2　nm　intermetallic　PdZn　nanoparticles,　by　employing　the　well-defined　porous　structures　of　calcinated　ZIF-8　(ZIF-8C)　and　an　in　situ　co-reduction　therein.　HAADF-STEM,　HRTEM,　and　EDS　characterizations　reveal　the　homogeneous　dispersion　of　these　sub-2　nm　intermetallic　PdZn　nanoparticles　within　the　ZIF-8C　frameworks.　XRD,　XPS,　and　EXAFS　measurements　further　confirm　the　atomically　ordered　intermetallic　phase　nature　of　these　sub-2　nm　PdZn　nanoparticles.　Selective　hydrogenation　of　acetylene　evaluation　results　show　the　excellent　catalytic　properties　of　the　sub-2　nm　intermetallic　PdZn,　which　result　from　the　energetically　more　favorable　path　for　acetylene　hydrogenation　and　ethylene　desorption　over　the　ultrasmall　particles　than　over　larger-sized　intermetallic　PdZn　as　revealed　by　density　functional　theory　(DFT)　calculations.　Moreover,　this　protocol　is　also　extendable　for　the　preparation　of　sub-2　nm　intermetallic　PtZn　nanoparticles　and　is　expected　to　provide　a　novel　methodology　in　synthesizing　ultrasmall　atomically　ordered　intermetallic　nanomaterials　by　rationally　functionalizing　MOFs.