A confined porphyrin Co(II), which is prepared by the following method: Equimolar amounts of aromatic aldehyde and pyrrole are condensed under acidic conditions to synthesize phenyl porphyrin compounds; the phenyl porphyrin compounds are metallized in a chloroform-methanol solution to obtain porphyrin Cu(II), which is brominated and demetallized to obtain confined porphyrin; the confined porphyrin is stirred and refluxed in a methanol solution for 12.0-24.0 h to obtain confined porphyrin Co(II). Its application is as follows: The confined porphyrin Co(II) is dissolved in cycloalkanes; the reaction system is sealed, and heated to 100 to 130° C. with stirring, to which oxygen is introduced to 0.2 to 3.0 MPa; the reaction is carried out for 3.0 to 24.0 h with stirring with the set temperature and oxygen pressure being maintained; and then the reaction solution is subjected to post-treatment to obtain the products.