NOVELTY - Scaffold material-transition metal hydride complexes (I) comprising scaffold material, and transition metal hydride (I-A) which is chemically bonded to functional groups formed on the surface of the scaffold material, are new.    USE - (I) are useful in gas storage (as hydrogen storage medium for operating medium to small sized fuel cells), as polymerization catalysts and optical isomers.    ADVANTAGE - (I) has high hydrogen storage capacity and efficiency with safety and reversibility, has enhanced chemical stability, does not disintegrates even with repeated adsorption-desorption of hydrogen, and can be prepared by relatively simple manufacturing system. (I) provides adsorption/desorption of hydrogen under relatively mild condition as compared conventional hydrogen storage materials.    DETAILED DESCRIPTION - Scaffold material-transition metal hydride complexes of formula ((SM)-M1-H(n-1)) (I) comprising scaffold material, and transition metal hydride of formula (M1-H(n-1)) (I-A) which is chemically bonded to functional groups formed on the surface of the scaffold material, are new.    SM = scaffold material containing functional groups on the surface;    M1 = transition metal having the valency of at least 2; and    n = valency of M1.    INDEPENDENT CLAIMS are also included for:    (1) the preparations of (I);    (2) scaffold material-transition metal halide complexes of formula ((SM)-M1-X(n-1)) (II) comprising a scaffold material and transition metal halide of formula (M1-X(n-1)) (II-A), which is chemically bonded to functional groups formed on the surface of the scaffold material;    (3) preparing (II) comprising reacting a scaffold material containing functional groups formed on the surface with transition metal halide of formula (M1-Xn) (II-B) forming a linkage of transition metal halide on the functional group to give (II);    (4) scaffold material-transition metal ligand complexes of formula ((SM)-M1-L(n-1)) (III) comprising scaffold material and transition metal ligand of formula (M1-L(n-1)) (III-A), which is chemically bonded to functional groups formed on the surface of the scaffold material; and    (5) preparing (III) comprising reacting a scaffold material containing a functional group formed on the surface with an organic-transition metal precursor of formula (M1-Ln) (III-B) forming a linkage of transition metal ligand to the functional groups to give (III).    X = halo; and    L = organic ligand (optionally linked each other to be chelated to metal as a bidentate or tridentate ligand).