A process for producing diazomethane of Formula 1 (CH2N2), with an automated apparatus is described. A stock solution of N-methyl-N-nitroso amine in an organic solvent is continuously flown and mixed with an aqueous inorganic base at a T-mixer to form a mixture. Then it is passed through a capillary micro reactor at a temperature in a range of 20 to 30° C. to form diazomethane. The mixture is separated into an aqueous layer and an organic layer using a continuous flow micro-separator. The organic layer has 0.1-0.4 M diazomethane. The organic layer is reacted with a carboxylic acid, phenol, an alkyne, an anhydride, a carboxyl metal organic framework (MOF), or MOF coated cotton to form a corresponding ester, a pyrazole, an ether, a diazo ketone, a stable carboxyl MOF or a stable MOF coated cotton fiber.