Calcium l‑Lactate Frameworks as Naturally Degradable Carriers for Pesticides

Two porous, chiral
metal–organic frameworks (MOFs), Ca14(l-lactate)20(acetate)8(C2H5OH)­(H2O) (MOF-1201) and Ca6(l-lactate)3(acetate)9(H2O) (MOF-1203), are constructed
from Ca2+ ions and l-lactate [CH3CH­(OH)­COO–], where
Ca2+ ions are bridged by the carboxylate and hydroxyl groups
of lactate and the carboxylate group of acetate to give a three-dimensional
arrangement of Ca­(−COO, −OH) polyhedra supporting one-dimensional
pores with apertures and internal diameters of 7.8 and 9.6 Å
(MOF-1201) and 4.6 and 5.6 Å (MOF-1203), respectively. These
MOFs represent the first examples of extended porous structures based
on Ca2+ and lactate. They show permanent porosity of 430
and 160 m2 g–1, respectively, and can
encapsulate an agriculturally important fumigant, cis-1,3-dichloropropene. MOF-1201 shows a 100 times lower release rate
compared with liquid cis-1,3-dichloropropene under
the same test conditions (25 °C, air flow rate of 1 cm3 min–1). The hydrolysis of MOF-1201 in water makes
it the first example of a degradable porous solid carrier for such
fumigants.