Molecular sieve desiccants are zeolite material with pores of uniform sizes. They efficiently adsorb gases and liquids based on their molecular size and polarity. Being a potential adsorbent for different liquids and gases, molecular sieve desiccants find their application in the steel production process, drying the inner space of the insulated glass window, filtration of oxygen in breathing apparatuses and air conditioning filter cores in our cars. It is used as a cost-effective and safe alternative in various applications in the chemical process industry. Based on the pore size, molecular sieve desiccants are mainly differentiated into four types: 3A, 4A, 5A, and 13X. The 3A molecular sieve desiccants find major application in petroleum and chemical industries for refining oil, polymerization, and chemical gas-liquid depth drying. The 3A and 4A molecular sieves can adsorb air contaminants, water or carbon dioxide powerfully. Due to the high performance and renewability of these desiccants, the lithium hydrogen canisters have been replaced by molecular sieve for carbon dioxide removal from the spacecraft cabin atmosphere.