Zeolitic　imidazolate　framework　(ZIF)　membranes　have　great　potential　applications　in　nanofiltration.　However,　preparing　continuous　and　intact　ZIF　membranes　on　the　surface　of　a　substrate　remains　challenging.　In　this　study,　we　assembled　ZIF-8　nanoparticles　in　situ　in　the　pores　of　a　porous　alumina　substrate　via　a　freezing-assisted　counter-diffusion　method.　Although　a　continuous　ZIF-8　membrane　was　not　formed　on　the　surface　of　the　sub-strate,　the　obtained　nano-confined　composite　membrane　was　dense　enough　to　separate　antibiotics　and　salt.　The　rejection　rate　of　tetracycline　was　above　99　%,　while　that　of　sodium　chloride　was　below　20　%,　demonstrating　good　antibiotic　desalination　performance.　The　permeance　of　the　ZIF-8　membrane　reached　23.5　LMH/bar.　Due　to　the　nano-confined　structure,　the　obtained　ZIF-8　composite　membrane　was　robust.　Besides,　polishing　the　surface　layer　did　not　reduce　the　separation　performance.　Moreover,　sulfurizing　the　ZIF-8　membrane　improved　its　sta-bility　in　water.　It　also　improved　the　permeance　to　31.3　LMH/bar,　which　remained　stable　for　100　h.　Therefore,　the　obtained　robust　ZIF-8　membrane　and　its　derivative　composite　membrane　fabricated　via　freezing-assisted　counter-diffusion　have　great　potential　in　antibiotic　desalination.