Assembly reactions of 5-(isonicotinamido)isophthalic acid (H₂INAIP) with Ln₂O₃ or Ln(NO₃)₃·6H₂O together with NaOH in the presence of AgNO₃ result in formation of two series of new 4d–4f heterometallic coordination polymers {[LnAg(INAIP)₂]·3H₂O}_n [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5)] and {[LnAg(INAIP)₂(H₂O)]·xH₂O}_n [Ln = La (6), Pr (7), Nd (8), x = 0; Dy (9), Er (10), x = 1]. The results of single-crystal X-ray diffraction analysis indicate that 1–5 are isomorphous and have 2-fold interpenetrated 3D structure with 3-nodal net Point (Schläfli) symbol for net: (4·6²)₄(4⁴·6⁶·8¹⁵·10³), while 6–10 are isostructural with similar non-interpenetrating 3D frameworks containing 2D lanthanide–carboxylate bilayers. The results indicate that the reaction conditions have great influence on the structure of the resulting complexes in this system. Furthermore, 3 and 5 show intense red and green fluorescent emissions, respectively, and the emission bands of Nd(III) were observed in the near IR region for 1. The magnetic properties of 1–5, 9 and 10 were investigated.