An iridium-porphyrin ligand, Ir(TCPP)Cl (TCPP = tetrakis(4-carboxyphenyl)porphyrin), has been utilized to react with HfCl4 to generate a stable Ir(iii)-porphyrin metal-organic framework of the formula [(Hf6(μ3-O)8(OH)2(H2O)10)2(Ir(TCPP)Cl)3]·solvents (Ir-PMOF-1(Hf)), which possesses two types of open cavities (1.9 × 1.9 × 1.9 and 3.0 × 3.0 × 3.0 nm3) crosslinked through orthogonal channels (1.9 × 1.9 nm2) in three directions. The smaller cavity is surrounded by four catalytic Ir(TCPP)Cl walls to form a confined coordination space as a molecular nanoreactor, while the larger one facilitates reactant/product feeding and release. Therefore, the porous Ir-PMOF-1(Hf) can act as a multi-channel crystalline molecular flask to promote the carbenoid insertion reaction into Si-H bonds, featuring high chemoselectivity towards primary silanes among primary, secondary and tertiary silanes under heterogeneous conditions that are inaccessible by conventional homogeneous catalysts.