Abstract: A heat-expandable microcapsule comprising a polymer shell formed by polymerizing (I) acrylonitrile, a main monomer component, (II) a monomer having carboxyl and (III) a monomer having groups reactive with the carboxyl of the monomer (II) and of a liquid having a boiling point lower than the softening point of the polymer and being encapsulated in the polymer shell. The heat-expandable microcapsules expand within high temperature range, 240° C. or above, and have heat-resistance.

Abstract: Disclosed are an adsorbent for CO, comprising a composite comprised of a porous inorganic carrier and, carried thereon, a binary complex of a nitrogen-containing compound and a copper(I) halide, the nitrogen-containing compound being at least one member selected from at least one pyridine compound and a diamine represented by R.sup.1 R.sup.2 N(CH.sub.2).sub.n --NR.sup.3 R.sup.4, wherein n is 2 or 3 and each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently represents a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group, with the proviso that when n is 2, each of at least two of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represents a C.sub.1 -C.sub.4 alkyl group atoms and that when n is 3, at least one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represents a C.sub.1 -C.sub.4 alkyl group, and a method for separating carbon monoxide by adsorption using the adsorbent.