Reactions of ZrCl(4) and single or mixed linear dicarboxylic acids bearing methyl or azide groups lead to highly stable isoreticular metal-organic frameworks (MOFs) with content-tunable, accessible, reactive azide groups inside the large pores. These Zr-based MOFs offer an ideal platform for pore surface engineering by anchoring various functional groups with controlled loadings onto the pore walls via the click reaction, endowing the MOFs with tailor-made interfaces. Significantly, the framework and crystallinity of the functionalized MOFs are well-retained, and the engineered pore surfaces have been demonstrated to be readily accessible, thus providing more opportunities for powerful and broad applications of MOFs.