NOVELTY - A metal-organic framework-based mesh-adjustable molecular sieve (I) comprising several first secondary building unit having metal clusters, and several second secondary building unit having amphiphilic ligands containing hydrophobic moiety and a functionalized hydrophilic moiety, is new. The metal clusters are bound with several amphiphilic ligand functionalized hydrophilic moieties to form a metal cluster layer. The metal cluster layer forms at least one hydrophilic pore.    USE - For separating gaseous molecules; and for adsorbing a molecular species selected from hydrogen, nitrogen, oxygen, cobalt, argon, methane, ethane, and propane (all claimed).    ADVANTAGE - The metal-organic framework-based mesh-adjustable molecular sieve exhibits a temperature-dependent mesh size of 2.9-5 Angstrom ; and exhibits a temperature-dependent molecular gating effect.    DETAILED DESCRIPTION - A metal-organic framework-based mesh-adjustable molecular sieve (I) comprising several first secondary building unit having metal clusters, and several second secondary building unit having amphiphilic ligands containing hydrophobic moiety and a functionalized hydrophilic moiety, is new. The metal clusters are bound with several amphiphilic ligand functionalized hydrophilic moieties to form a metal cluster layer. The metal cluster layer forms at least one hydrophilic pore. On each side of the metal cluster layer, several associated amphiphilic ligand hydrophobic moieties cooperate with the metal cluster layer to form a tri-layer. The tri-layers are packed in a facing, spaced-apart relationship to form at least one hydrophobic pore. INDEPENDENT CLAIMS are included for the following:    (1) preparation of metal-organic framework-based mesh-adjustable molecular sieve (I);    (2) separating gaseous molecules comprising contacting the metal-organic framework-based mesh-adjustable molecular sieve (I) with a mixture of molecules selected from hydrogen/nitrogen, hydrogen/carbon monoxide, nitrogen/oxygen, nitrogen/methane, methane/ethane and ethane/propane, where the molecules are separated from their respective pair;    (3) adsorbing (P1) a molecular species selected from hydrogen, nitrogen, oxygen, cobalt, argon, methane, ethane, and propane involving contacting the metal-organic framework-based mesh-adjustable molecular sieve (I) with a mixture of molecular species containing one of hydrogen, nitrogen, oxygen, carbon monoxide, argon, methane, ethane and propane;    (4) 4'-methyl-biphenyl-3,5-dicarboxylic acid is new;    (5) preparation of 4'-methyl-biphenyl-3,5-dicarboxylic acid involves reacting isophthalic acid with silver sulfate in the presence of sulfuric acid and bromine to obtain 5-bromo-isophthalic acid, reacting 5-bromo-isophthalic acid with methyl alcohol in the presence of sulfuric acid to obtain 5-bromo-isophthalic acid dimethyl ester, followed by reacting with B(OCH3)3 and then Pd(PPh3)4 to obtain 4'-methyl-biphenyl-3,5-dicarboxylic acid dimethyl ester; and then 4'-methyl-biphenyl-3,5-dicarboxylic acid dimethyl ester with sodium hydroxide to obtain 4'-methyl-biphenyl-3,5-dicarboxylic acid;    (6) dicarboxylate ion of 4'-methyl-biphenyl-3,5-dicarboxylate of the acid is new;    (7) 4'-tert-butyl-biphenyl-3,5-dicarboxylic acid is new;    (8) dicarboxylate ion of 4'-tert-butyl-biphenyl-3,5-dicarboxylate of the acid is new;    (9) preparation of 4'-tert-butyl-biphenyl-3,5-dicarboxylic acid involves reacting isophthalic acid with silver sulfate in the presence of sulfuric acid and bromine to obtain 5-bromo-isophthalic acid, reacting 5-bromo-isophthalic acid with methyl alcohol in the presence of sulfuric acid to obtain 5-bromo-isophthalic acid dimethyl ester, followed by reacting with B(OCH3)3 and then Pd(PPh3)4 to obtain 4'-isopropyl-biphenyl-3,5-dicarboxylic acid dimethyl ester, and then 4'-isopropyl-biphenyl-3,5-dicarboxylic acid dimethyl ester with sodium hydroxide to obtain 4'-tert-butyl-biphenyl-3,5-dicarboxylic acid.